Data transfer method and data transfer apparatus for image reading apparatus and image reading apparatus with data transfer apparatus

ABSTRACT

A data transfer method and apparatus for an image reading apparatus suitably used with an image scanner is improved in that a transfer line apparatus is simplified in construction and produced with a reduced cost by an improved transferring technique of data. The data transfer apparatus is incorporated in an image reading apparatus including first and second optical image reading units and comprises a storage section for storing data from a first operating one of the first and second optical image reading units from which paper image information is to be read out later, a first data transfer section for successively transferring, by way of a data transfer line, data from the first operating image reading unit, and a second data transfer section for successively transferring, after the data from the first operating image reading unit have been transferred by the first data transfer means, the data from the other later operating image reading unit stored in the storage means at a rate higher than the data transfer rate at which data are transferred by the first data transfer means by way of the data transfer line.

This application is a continuation of application Ser. No. 08/407,471filed Mar. 20, 1995, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a data transfer method and a data transferapparatus for an image reading apparatus which is suitably used with animage scanner and an image apparatus with such data transfer apparatus.

2. Description of the Related Art

In recent years, image reading apparatus as image inputting apparatussuch as image scanners have been and are being developed in order toinput image information to a computer (host computer) or a likeapparatus.

Some of image reading apparatus conventionally proposed include a pairof optical image reading units for optically reading front face imageinformation and rear face image information of a paper sheet. In animage reading apparatus of the both face reading type just mentioned,data from the image reading units are processed independently of eachother and then sent to a host computer by way of independent transferlines. In particular, a data output port of the apparatus has twoconnectors, from which different data are extracted and sent to the hostcomputer.

With the conventional apparatus, however, because data from the imagereading units are processed independently of each other and sent to ahost computer by way of independent transfer lines, and particularlybecause two systems of transfer lines are connected to the connectors,there is a subject to be solved in that the transfer lines arecomplicated and a high cost is required.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a data transfermethod and a data transfer apparatus wherein a transfer line apparatusis simplified in construction and produced with a reduced cost by animproved transferring technique of data and an image reading apparatuswith such data transfer apparatus.

In order to attain the object described above, according to an aspect ofthe present invention, there is provided a data transfer method for animage reading apparatus which includes a first optical image readingunit located at a location along a paper transport path for opticallyreading front face image information from a paper sheet transportedalong the paper transport path, and a second optical image reading unitlocated at another location along the paper transport path for opticallyreading rear face image information from the paper sheet transportedalong the paper transport path, comprising the steps of successivelytransferring, by way of a data transfer line, data from a firstoperating image reading unit from one of the first optical image readingunit and the second optical image reading unit from which paper imageinformation is to be read out first, temporarily storing data from alater operating image reading unit from one of the first optical imagereading unit and the second optical image reading unit from which paperimage information is to be read out later, and successivelytransferring, after the data from one of the operating image readingunits have been transferred, the stored data from the later operatingimage reading unit at a rate higher than the transfer rate at which thedata from one of the operating image reading units have beentransferred.

In the data transfer method, data from one of the operating imagereading units are successively transferred by way of the data transferline, and then, data from the later operating image reading unit aretemporarily stored once and then successively transferred, after thedata from one of the first operating image reading unit is transferred,at the rate higher than the transfer rate of the data from the firstoperating image reading unit by way of the data transfer line.Accordingly, even if image reading by the later operating image readingunit is started before image reading by the one of the operating imagereading unit is completed, data during the overlapping period of timecan be held with certainty, and besides, data from the later operatingimage reading unit which are to be transferred later can be transferredrapidly to the host computer side. Consequently, even where the imagereading units are disposed in the proximity of the paper transport pathin order to achieve minimization, reduction in weight and compaction ofthe apparatus, data of the front and rear faces of a paper sheet can betransferred to the host computer side before the paper sheet isdischarged to a stacking mechanism. Consequently, even if paper sheetsare successively transferred at a high speed while achievingminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of each paper sheet can be read andtransferred to the host computer side satisfactorily.

The data from the later operating image reading unit may be stored forone full paper sheet. This facilitates memory control.

Alternatively, data from the later operating image reading unit may beheld stored until the data from the later operating image reading unitare permitted to be transferred through the image reading apparatusafter outputting of the data from the first operating image reading unitfor one full paper sheet has been completed. This can reduce the memorycapacity.

Completion of transfer of the data from the first operating imagereading unit may be detected based on paper trailing end detectioninformation. This allows a wide variety of paper sheets of various sizesto be transported in the image reading apparatus comparatively readilyin order to read information on them.

According to another aspect of the present invention, there is provideda data transfer apparatus for an image reading apparatus which includesa first optical image reading unit located at a location along a papertransport path for optically reading front face image information from apaper sheet transported along the paper transport path, and a secondoptical image reading unit located at another location along the papertransport path for optically reading rear face image information fromthe paper sheet transported along the paper transport path, comprisingstorage means for storing data from a later operating image reading unitfrom one of the first optical image reading unit and the second opticalimage reading unit from which paper image information is to be read outlater, first data transfer means for successively transferring, by wayof a data transfer line, data from a first operating image reading unitfrom one of the first optical image reading unit and the second opticalimage reading unit from which paper image information is to be read outfirst, and second data transfer means for successively transferring,after the data from the first operating image reading unit have beentransferred by the first data transfer means, the data from the lateroperating image reading unit stored in the storage means at a ratehigher than the data transfer rate at which data are transferred by thefirst data transfer means by way of the data transfer line.

In the data transfer apparatus, data from the first operating imagereading unit are successively transferred by way of the data transferline by the first data transfer means, and then, data from the lateroperating image reading unit are temporarily stored into the storagemeans once and then successively transferred, after the data from thefirst operating image reading unit are transferred, at the rate higherthan the transfer rate of the data from the first operating imagereading unit by way of the data transfer line by the second datatransfer means. Accordingly, even if image reading by the lateroperating image reading unit is started before image reading by thefirst operating image reading unit is completed, data during theoverlapping period of time can be held with certainty, and besides, datafrom the later operating image reading unit which are to be transferredlater can be transferred rapidly to the host computer side.Consequently, even where the image reading units are disposed in theproximity of the paper transport path in order to achieve minimization,reduction in weight and compaction of the apparatus, data of the frontand rear faces of a paper sheet can be transferred to the host computerside before the paper sheet is discharged to a stacking mechanism.Consequently, even if paper sheets are successively transferred at ahigh speed while achieving minimization, reduction in weight andcompaction of the apparatus, data of the front and rear faces of eachpaper sheet can be read and transferred to the host computer sidesatisfactorily.

The data transfer apparatus for an image reading apparatus may furthercomprise auxiliary storage means for storing partial paper imageinformation read out from the storage means between successive writingoperations of data into the storage means. Where such auxiliary storagemeans is provided, data can be read out little by little from thestorage means while giving priority to writing into the storage means,and consequently, the data transfer time can be reduced.

According to a further aspect of the present invention, there isprovided an image reading apparatus with a data transfer apparatus,comprising a first optical image reading unit located at a locationalong a paper transport path for optically reading front face imageinformation from a paper sheet transported along the paper transportpath, a second optical image reading unit located at another locationalong the paper transport path for optically reading rear face imageinformation from the paper sheet transported along the paper transportpath, and a data transfer apparatus for transferring paper imageinformation from the first optical image reading unit and the secondoptical image reading unit, the data transfer apparatus includingstorage means for storing data from a later operating image reading unitfrom one of the first optical image reading unit and the second opticalimage reading unit from which paper image information is to be read outlater, first data transfer means for successively transferring, by wayof a data transfer line, data from a first operating image reading unitfrom between the first optical image reading unit and the second opticalimage reading unit from which paper image information is to be read outfirst, and second data transfer means for successively transferring,after the data from the first operating image reading unit have beentransferred by the first data transfer means, the data from the lateroperating image reading unit stored in the storage means at a ratehigher than the data transfer rate at which data are transferred by thefirst data transfer means by way of the data transfer line.

In the image reading apparatus with a data transfer apparatus, data fromthe first operating image reading unit are successively transferred byway of the data transfer line by the first data transfer means, andthen, data from the later operating image reading unit are temporarilystored into the storage means once and then successively transferred,after the data from the first operating image reading unit aretransferred, at the rate higher than the transfer rate of the data fromthe first operating image reading unit by way of the data transfer lineby the second data transfer means. Accordingly, even if image reading bythe later operating image reading unit is started before image readingby the first operating image reading unit is completed, data during theoverlapping period of time can be held with certainty, and besides, datafrom the later operating image reading unit which are to be transferredlater can be transferred rapidly to the host computer side.Consequently, even where the image reading units are disposed in theproximity of the paper transport path in order to achieve minimization,reduction in weight and compaction of the apparatus, data of the frontand rear faces of a paper sheet can be transferred to the host computerside before the paper sheet is discharged to a stacking mechanism.Consequently, even if paper sheets are successively transferred at ahigh speed while achieving minimization, reduction in weight andcompaction of the apparatus, data of the front and rear faces of eachpaper sheet can be read and transferred to the host computer sidesatisfactorily.

According to a still further aspect of the present invention, there isprovided a data transfer method for an image reading apparatus whichincludes a first optical image reading unit located at a location alonga paper transport path for optically reading front face imageinformation from a paper sheet transported along the paper transportpath, and a second optical image reading unit located at anotherlocation along the paper transport path for optically reading rear faceimage information from the paper sheet transported along the papertransport path, comprising the steps of temporarily storing data fromthe first optical image reading unit and the second optical imagereading unit, reading out the stored data obtained from one of the firstoptical image reading unit and the second optical image reading unit ata reading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of a data transfer line, and reading out the stored data obtainedfrom the other of the first optical image reading unit and the secondoptical image reading unit at a reading out rate higher than the writingrate at which the stored data have been stored and successivelytransferring the thus read out data by way of the data transfer line.

In the data transfer method, data from the first operating image readingunit and the second operating image reading unit are temporarily storedonce, and then the stored data obtained from one of the first opticalimage reading unit and the second optical image reading unit are readout at the reading out rate higher than the writing rate andsuccessively transferred by way of the data transfer line, whereafterthe stored data obtained from the other of the first optical imagereading unit and the second optical image reading unit are read out atthe reading out rate higher than the writing rate and successivelytransferred by way of the data transfer line. Accordingly, even if imagereading by the later operating image reading unit is started beforeimage reading by the first operating image reading unit is completed,data during the overlapping period of time can be held with certainty,and besides, data from the later operating image reading unit which areto be transferred later can be transferred rapidly to the host computerside. Consequently, even where the image reading units are disposed inthe proximity of the paper transport path in order to achieveminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of a paper sheet can be transferred to thehost computer side before the paper sheet is discharged to a stackingmechanism. Consequently, even if paper sheets are successivelytransferred at a high speed while achieving minimization, reduction inweight and compaction of the apparatus, data of the front and rear facesof each paper sheet can be read and transferred to the host computerside satisfactorily.

A plurality of data may be obtained from each of the first optical imagereading unit and the second optical image reading unit. This allows thedata transfer method to be applied to transfer of read data of, forexample, a color original.

According to a yet further aspect of the present invention, there isprovided a data transfer apparatus for an image reading apparatus whichincludes a first optical image reading unit located at a location alonga paper transport path for optically reading front face imageinformation from a paper sheet transported along the paper transportpath, and a second optical image reading unit located at anotherlocation along the paper transport path for optically reading rear faceimage information from the paper sheet transported along the papertransport path, comprising first storage means for storing data from thefirst optical image reading unit, second storage means for storing datafrom the second optical image reading unit, first data transfer meansfor reading out the stored data obtained from one of the first opticalimage reading unit and the second optical image reading unit at areading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of a data transfer line, and second data transfer means for readingout, after the data stored in the first storage means have beentransferred by the first data transfer means, the stored data obtainedfrom the other of the first optical image reading unit and the secondoptical image reading unit at a reading out rate higher than the writingrate at which the stored data have been stored and successivelytransferring the thus read out data by way of the data transfer line.

In the data transfer apparatus, data from the first operating imagereading unit and the second operating image reading unit are temporarilystored once into the first storage means and the second storage means,respectively, and then the stored data obtained from one of the firstoptical image reading unit and the second optical image reading unit areread out at the reading out rate higher than the writing rate andsuccessively transferred by way of the data transfer line, whereafterthe stored data obtained from the other of the first optical imagereading unit and the second optical image reading unit are read out atthe reading out rate higher than the writing rate and successivelytransferred by way of the data transfer line. Accordingly, even if imagereading by the later operating image reading unit is started beforeimage reading by the first operating image reading unit is completed,data during the overlapping period of time can be held with certainty,and besides, data from the later operating image reading unit which areto be transferred later can be transferred rapidly to the host computerside. Consequently, even where the image reading units are disposed inthe proximity of the paper transport path in order to achieveminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of a paper sheet can be transferred to thehost computer side before the paper is sheet is discharged to a stackingmechanism. Consequently, even if paper sheets are successivelytransferred at a high speed while achieving minimization, reduction inweight and compaction of the apparatus, data of the front and rear facesof each paper sheet can be read and transferred to the host computerside satisfactorily.

According to a yet further aspect of the present invention, there isprovided an image reading apparatus with a data transfer apparatus,comprising a first optical image reading unit located at a locationalong a paper transport path for optically reading front face imageinformation from a paper sheet transported along the paper transportpath, a second optical image reading unit located at another locationalong the paper transport path for optically reading rear face imageinformation from the paper sheet transported along the paper transportpath, and a data transfer apparatus for transferring paper imageinformation from the first optical image reading unit and the secondoptical image reading unit, the data transfer apparatus including firststorage means for storing data from the first optical image readingunit, second storage means for storing data from the second opticalimage reading unit, first data transfer means for reading out the storeddata obtained from one of the first optical image reading unit and thesecond optical image reading unit at a reading out rate higher than thewriting rate at which the stored data have been stored and successivelytransferring the thus read out data by way of a data transfer line, andsecond data transfer means for reading out, after the data stored in thefirst storage means have been transferred by the first data transfermeans, the stored data obtained from the other of the first opticalimage reading unit and the second optical image reading unit at areading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of the data transfer line.

In the image reading apparatus with a data transfer apparatus, data fromthe first operating image reading unit and the second operating imagereading unit are temporarily stored once into the first storage meansand the second storage means, respectively, and then the stored dataobtained from one of the first optical image reading unit and the secondoptical image reading unit are read out at the reading out rate higherthan the writing rate and successively transferred by way of the datatransfer line, whereafter the stored data obtained from the other of thefirst optical image reading unit and the second optical image readingunit are read out at the reading out rate higher than the writing rateand successively transferred by way of the data transfer line.Accordingly, even if image reading by the later operating image readingunit is started before image reading by the first operating imagereading unit is completed, data during the overlapping period of timecan be held with certainty, and besides, data from the later operatingimage reading unit which are to be transferred later can be transferredrapidly to the host computer side. Consequently, even where the imagereading units are disposed in the proximity of the paper transport pathin order to achieve minimization, reduction in weight and compaction ofthe apparatus, data of the front and rear faces of a paper sheet can betransferred to the host computer side before the paper sheet isdischarged to a stacking mechanism. Consequently, even if paper sheetsare successively transferred at a high speed while achievingminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of each paper sheet can be read andtransferred to the host computer side satisfactorily.

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts orelements are denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view illustrating an aspect of the presentinvention;

FIG. 2 is a similar view illustrating another aspect of the presentinvention;

FIG. 3 is a block diagram of an image data processing system showing apreferred embodiment of the present invention;

FIG. 4 is a schematic side elevational sectional view of an imagereading apparatus to which the image data processing system isincorporated;

FIG. 5 is a perspective view showing an outer profile of the imagereading apparatus of FIG. 4;

FIG. 6 is a schematic side elevational view showing an outer profile ofthe image reading apparatus of FIG. 4;

FIG. 7 is a diagrammatic view schematically showing, in side elevation,an arrangement of principal components of the image reading apparatus ofFIG. 4;

FIG. 8 is an exploded perspective view schematically showing a drivingsystem of the image reading apparatus of FIG. 4;

FIG. 9 is a diagrammatic view schematically showing, in side elevation,the driving system shown in FIG. 8;

FIG. 10 is a diagrammatic view schematically showing, in plan, thedriving system shown in FIG. 8;

FIGS. 11(A) and 11(B) are a schematic plan view and a schematic sideelevational view, respectively, showing a paper transport system of theimage reading apparatus of FIG. 4;

FIG. 12 is a schematic side elevational view showing the construction ofan image reading mechanism of the image reading apparatus of FIG. 4;

FIG. 13 is a diagrammatic view schematically showing the construction ofthe optical image reading mechanism shown in FIG. 12;

FIG. 14 is a block diagram showing the construction of a white levelinformation correction apparatus to which the present invention isapplied together with several associated elements;

FIG. 15 is a block diagram showing a white level algorithm circuit ofthe white level information correction apparatus shown in FIG. 14;

FIG. 16 is a block diagram showing another form of the white levelalgorithm circuit of the white level information correction apparatusshown in FIG. 14;

FIG. 17 is a block diagram showing a further form of the white levelalgorithm circuit of the white level information correction apparatusshown in FIG. 14;

FIG. 18 is a time chart illustrating operation of the while levelinformation correction apparatus shown in FIG. 14;

FIG. 19 is a block diagram showing the construction of another whitelevel information correction apparatus to which the present invention isapplied together with several associated elements;

FIG. 20 is a block diagram showing the construction of a further whitelevel information correction apparatus to which the present invention isapplied together with several associated elements;

FIG. 21 is a block diagram showing the construction of an outputtingsection and an output control circuit of the image data processingsystem shown in FIG. 2;

FIG. 22 is a flow chart illustrating operation of the outputting sectionand the output control section shown in FIG. 21;

FIG. 23 is a block diagram showing the construction of an original enddetection circuit of the image data processing system shown in FIG. 2;

FIG. 24 is a time chart illustrating operation of the original enddetection circuit shown in FIG. 23;

FIG. 25 is a sequence diagram illustrating initialization operation of ahopper system of the image reading apparatus of FIG. 4;

FIG. 26 is a sequence diagram illustrating operation of the hoppersystem in an automatic reading mode;

FIG. 27 is a sequence diagram illustrating operation of the hoppersystem in a manual insertion mode;

FIG. 28 is a sequence diagram illustrating operation of a transportsystem of the image reading apparatus of FIG. 4;

FIG. 29 is a similar view but illustrating operation of the transportsystem at a different stage;

FIG. 30 is a similar view but illustrating operation of the transportsystem at another different stage;

FIG. 31 is a front elevational view showing an operation panel of theimage reading apparatus shown in FIG. 4;

FIG. 32 is a block diagram schematically showing the construction of acontrol system of the image reading apparatus shown in FIG. 4;

FIG. 33 is a diagrammatic view of another image data processing systemshowing another preferred embodiment of the present invention;

FIG. 34 is a block diagram showing an outputting section and an outputcontrol circuit of the image data processing system shown in FIG. 33;and

FIGS. 35 and 36 are flow charts illustrating operation of the outputtingsection and the output control circuit shown in FIG. 34.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

a. Aspects of the Invention

Referring first to FIG. 1, there is shown an image reading apparatuswith a data transfer apparatus according to an aspect of the presentinvention. The image reading apparatus includes a paper transport path310 for transporting a paper sheet 40 from which an image is to be read,a first optical image reading unit 412 located at a location along thepaper transport path 310 for optically reading front face imageinformation from a paper sheet 40 transported along the paper transportpath 310, and a second optical image reading unit 414 located at anotherlocation along the paper transport path 310 for optically reading rearface image information from the paper sheet 40 transported along thepaper transport path 310.

The image reading apparatus is provided with a data transfer apparatus160 for transferring paper image information from the first opticalimage reading unit 412 and the second optical image reading unit 414.The data transfer apparatus 160 includes storage means 161, first datatransfer means 163, and second data transfer means 164.

The storage means 161 stores data from a later operating image readingunit from one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out later.

The first data transfer means 163 successively transfers, by way of adata transfer line 165, data from a first operating image reading unitfrom one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out first.

The second data transfer means 164 successively transfers, after thedata from the first operating image reading unit have been transferredby the first data transfer means 163, the data from the later operatingimage reading unit stored in the storage means 161 at a rate higher thanthe data transfer rate at which data are transferred by the first datatransfer means 163 by way of the data transfer line 165.

The data transfer apparatus 160 further comprises auxiliary storagemeans 162 for storing partial paper image information read out from thestorage means 161 between successive writing operations of data into thestorage means 161.

Further, a method according to the present invention is applied to suchan image reading apparatus as shown in FIG. 1 which includes a firstoptical image reading unit 412 located at a location along a papertransport path 310 for optically reading front face image informationfrom a paper sheet 40 transported along the paper transport path 310,and a second optical image reading unit 414 located at another locationalong the paper transport path 310 for optically reading rear face imageinformation from the paper sheet 40 transported along the papertransport path 310, and comprises the steps of:

1-1. successively transferring, by way of a data transfer line 165, datafrom a first operating image reading unit from one of the first opticalimage reading unit 412 and the second optical image reading unit 414from which paper image information is to be read out first;

1-2. temporarily storing data from a later operating image reading unitfrom one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out later; and

1-3. successively transferring, after the data from the first operatingimage reading unit have been transferred, the stored data from the lateroperating image reading unit at a rate higher than the transfer rate atwhich the data from the first operating image reading unit have beentransferred.

In this instance, the data from the later operating image reading unitmay be stored for one full paper sheet or else may be held stored untilthe data from the later operating image reading unit are permitted to betransferred through the image reading apparatus after outputting of thedata from the first operating image reading unit for one full papersheet has been completed.

The data transfer method may further comprise the step of detectingcompletion of transfer of the data from the first operating imagereading unit based on paper trailing end detection information.

In the image reading apparatus shown in FIG. 1 which includes the firstoptical image reading unit 412 located at a location along the papertransport path 310 for optically reading front face image informationfrom a paper sheet 40 transported along the paper transport path 310 andthe second optical image reading unit 414 located at another locationalong the paper transport path 310 for optically reading rear face imageinformation from the paper sheet 40 transported along the papertransport path 310, data from the first operating image reading unitfrom one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out first are successively transferred by way of the datatransfer line 165 by the first data transfer means 163 (step 1-1), andthen, data from the later operating image reading unit from one of thefirst optical image reading unit 412 and the second optical imagereading unit 414 from which paper image information is to be read outlater are temporarily stored once into the storage means 161 (step 1-2),whereafter, after the data from the first operating image reading unithave been transferred, the stored data from the later operating imagereading unit are successively transferred by way of the data transferline 165 by the second data transfer means 164 at a rate higher than thetransfer rate at which the data from the first operating image readingunit have been transferred (step 1-3).

In this instance, the data from the later operating image reading unitare stored for one full paper sheet or else are held stored until thedata from the later operating image reading unit are permitted to betransferred through the image reading apparatus after outputting of thedata from the first operating image reading unit for one full papersheet has been completed.

Meanwhile, partial paper image information read out from the storagemeans 161 between successive writing operations of data into the storagemeans 161 is stored into the auxiliary storage means 162.

Further, completion of transfer of the data from the first operatingimage reading unit is detected based on paper trailing end detectioninformation.

According to the data transfer method, the data transfer apparatus foran image reading apparatus and the image reading apparatus with a datatransfer apparatus described above, the following effects or advantagesare achieved.

1. Since the data transfer apparatus for an image reading apparatus isconstructed such that it comprises the storage means 161 for storingdata from a later operating image reading unit from one of the firstoptical image reading unit 412 and the second optical image reading unit414 from which paper image information is to be read out later, thefirst data transfer means 163 for successively transferring, by way ofthe data transfer line 165, data from a first operating image readingunit from one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out first, and the second data transfer means 164 forsuccessively transferring, after the data from the first operating imagereading unit 412 have been transferred by the first data transfer means163, the data from the later operating image reading unit stored in thestorage means 161 at a rate higher than the data transfer rate at whichdata are transferred by the first data transfer means 163 by way of thedata transfer line 165 and that data from the first operating imagereading unit are successively transferred by way of the data transferline 165, and then, data from the later operating image reading unit aretemporarily stored once and then successively transferred, after thedata from the first operating image reading unit are transferred, at therate higher than the transfer rate of the data from the first operatingimage reading unit by way of the data transfer line, even if imagereading by the later operating image reading unit is started beforeimage reading by the first operating image reading unit is completed,data during the overlapping period of time can be held with certainty,and besides, data from the later operating image reading unit which areto be transferred later can be transferred rapidly to the host computerside. Consequently, even where the image reading units are disposed inthe proximity of the paper transport path in order to achieveminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of a paper sheet can be transferred to thehost computer side before the paper sheet is discharged to a stackingmechanism. Consequently, even if paper sheets are successivelytransferred at a high speed while achieving minimization, reduction inweight and compaction of the apparatus, data of the front and rear facesof each paper sheet can be read and transferred to the host computerside satisfactorily.

2. Where the data from the later operating image reading unit are storedfor one full paper sheet, memory control is facilitated.

3. Where data from the later operating image reading unit are heldstored until the data from the later operating image reading unit arepermitted to be transferred through the image reading apparatus afteroutputting of the data from the first operating image reading unit forone full paper sheet has been completed, the memory capacity can bereduced.

4. Where completion of transfer of the data from the first operatingimage reading unit is detected based on paper trailing end detectioninformation, it is comparatively easy for a wide variety of paper sheetsof various sizes to be transported in the image reading apparatus inorder to read information on them.

5. Where the data transfer apparatus for an image reading apparatusfurther comprises the auxiliary storage means 162 for storing partialpaper image information read out from the storage means 161 betweensuccessive writing operations of data into the storage means 161, datacan be read out little by little from the storage means 161 while givingpriority to writing into the storage means 161, and consequently, thedata transfer time can be reduced.

Referring now to FIG. 2, there is shown an image reading apparatus witha data transfer apparatus according to another aspect of the presentinvention. The image reading apparatus includes a paper transport path310 for transporting a paper sheet 40 from which an image is to be read,a first optical image reading unit 412 located at a location along thepaper transport path 310 for optically reading front face imageinformation from a paper sheet 40 transported along the paper transportpath 310, and a second optical image reading unit 414 located at anotherlocation along the paper transport path 310 for optically reading rearface image information from the paper sheet 40 transported along thepaper transport path 310.

The image reading apparatus is provided with a data transfer apparatus160 for transferring paper image information from the first opticalimage reading unit 412 and the second optical image reading unit 414.The data transfer apparatus 160 includes first storage means 161A,second storage means 161B, first data transfer means 163, and seconddata transfer means 164.

The first storage means 161A stores data from the first optical imagereading unit 412, and the second storage means 161B stores data from thesecond optical image reading unit 414.

The first data transfer means 163 reads out the stored data obtainedfrom one of the first optical image reading unit 412 and the secondoptical image reading unit 414 at a reading out rate higher than thewriting rate at which the stored data have been stored, and successivelytransfers the thus read out data by way of a data transfer line 165.

The second data transfer means 164 reads out, after the data stored inthe first storage means 161A have been transferred by the first datatransfer means 163, the stored data obtained from the other of the firstoptical image reading unit 412 and the second optical image reading unit414 at a reading out rate higher than the writing rate at which thestored data have been stored, and successively transfers the thus readout data by way of the data transfer line 165.

Further, another method according to the present invention is applied tosuch an image reading apparatus as shown in FIG. 2 which includes afirst optical image reading unit 412 located at a location along a papertransport path 310 for optically reading front face image informationfrom a paper sheet 40 transported along the paper transport path 310,and a second optical image reading unit 414 located at another locationalong the paper transport path 310 for optically reading rear face imageinformation from the paper sheet 40 transported along the papertransport path 310, and comprises the steps of:

2-1: temporarily storing data from the first optical image reading unit412 and the second optical image reading unit 414;

2-2. reading out the stored data obtained from one of the first opticalimage reading unit 412 and the second optical image reading unit 414 ata reading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of a data transfer line 165; and

2-3. reading out the stored data obtained from the other of the firstoptical image reading unit 412 and the second optical image reading unit414 at a reading out rate higher than the writing rate at which thestored data have been stored and successively transferring the thus readout data by way of the data transfer line 165.

It is to be noted that a plurality of data may be obtained from each ofthe first optical image reading unit 412 and the second optical imagereading unit 414.

In the image reading apparatus shown in FIG. 2 which includes the firstoptical image reading unit 412 located at a location along the papertransport path 310 for optically reading front face image informationfrom a paper sheet 40 transported along the paper transport path 310 andthe second optical image reading unit 414 located at another locationalong the paper transport path 310 for optically reading rear face imageinformation from the paper sheet 40 transported along the papertransport path 310, data from the first optical image reading unit 412and the second optical image reading unit 414 are temporarily storedinto the first storage means 161A and the second storage means 161B,respectively (step 2-1), and then, the stored data obtained from one ofthe first optical image reading unit 412 and the second optical imagereading unit 414 are read out at a reading out rate higher than thewriting rate and successively transferred by way of the data transferline 165 by the first data transfer means 163 (step 2-2), whereafter thestored data obtained from the other of the first optical image readingunit 412 and the second optical image reading unit 414 are read out at areading out rate higher than the writing rate and successivelytransferred by way of the data transfer line 165 by the second datatransfer means 164.

In the data transfer method, a plurality of data may be obtained fromeach of the first optical image reading unit 412 and the second opticalimage reading unit 414.

According to the data transfer method, the data transfer apparatus foran image reading apparatus and the image reading apparatus with a datatransfer apparatus described above, the following effects or advantagesare achieved.

1. Since the data transfer apparatus is constructed such that itcomprises the first storage means 161A for storing data from the firstoptical image reading unit 412, the second storage means 161B forstoring data from the second optical image reading unit 414, the firstdata transfer means 163 for reading out the stored data obtained fromone of the first optical image reading unit 412 and the second opticalimage reading unit 414 at a reading out rate higher than the writingrate and successively transferring the thus read out data by way of thedata transfer line 165, and the second data transfer means 164 forreading out, after the data stored in the first storage means 161A havebeen transferred by the first data transfer means 163, the stored dataobtained from the other of the first optical image reading unit 412 andthe second optical image reading unit 414 at a reading out rate higherthan the writing rate and successively transferring the thus read outdata by way of the data transfer line 165 and that data from the firstoperating image reading unit 412 and the second operating image readingunit 414 are temporarily stored once and then the stored data obtainedfrom one of the first optical image reading unit 412 and the secondoptical image reading unit 414 are read out at the reading out ratehigher than the writing rate and successively transferred by way of thedata transfer line 165, whereafter the stored data obtained from theother of the first optical image reading unit 412 and the second opticalimage reading unit 414 are read out at the reading out rate higher thanthe writing rate and successively transferred by way of the datatransfer line 165, even if image reading by the later operating imagereading unit is started before image reading by the first operatingimage reading unit is completed, data during the overlapping period oftime can be held with certainty, and besides, data from the lateroperating image reading unit which are to be transferred later can betransferred rapidly to the host computer side. Consequently, even wherethe image reading units are disposed in the proximity of the papertransport path in order to achieve minimization, reduction in weight andcompaction of the apparatus, data of the front and rear faces of a papersheet can be transferred to the host computer side before the papersheet is discharged to a stacking mechanism. Consequently, even if papersheets are successively transferred at a high speed while achievingminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of each paper sheet can be read andtransferred to the host computer side satisfactorily.

2. Where a plurality of data are obtained from each of the first opticalimage reading unit 412 and the second optical image reading unit 414,the data transfer method can be applied to transfer of read data of, forexample, a color original.

b. Embodiment of the Invention

An image reading apparatus according to a preferred embodiment of thepresent invention will be described in detail below with reference tothe accompanying drawings.

1. General Construction of the Image Reading Apparatus

Referring first to FIGS. 4 to 7, there is shown an image readingapparatus according to a preferred embodiment of the present invention.The general structure of the image reading apparatus shown can bedivided into an apparatus body 10 and an apparatus lid unit 20. Theapparatus lid unit 20 is mounted for pivotal motion around a fulcrum 32to open or close the apparatus body 10. When the image reading apparatusis used, the apparatus lid unit 20 is fixed to such a closing conditionas indicated by solid lines in FIGS. 4 to 6 by a body-lid unit lockingmechanism 30. Various other components of the image reading apparatusare mounted on the apparatus body 10 and the apparatus lid unit 20.

Referring to FIGS. 4 and 7, the image reading apparatus includes, ascomponents thereof, a paper supply mechanism 200 which can successivelysupply paper sheets 40 accommodated therein, a paper transport mechanism300 for transporting a paper sheet 40 supplied from the paper supplymechanism 200, an optical image reading mechanism 400 for opticallyreading information on a paper sheet 40 being transported by the papertransport mechanism 300, and a paper stacking mechanism 500 forreceiving a paper sheet 40 discharged from the paper transport mechanism300 to stack such paper sheets 40.

The paper supply mechanism 200 includes a paper supply hopper 210 whichcan accommodate therein paper sheets 40 to be read, a paper supplyroller 220 located above the paper supply hopper 210 for supplying oneof paper sheets 40 accommodated in the paper supply hopper 210 towardthe paper transport mechanism 300, a paper supply roller drivingmechanism 230 for driving the paper supply roller 220 to rotate, a papersupply hopper driving mechanism 240 for driving the paper supply hopper210 to an inclined position in response to the amount of paper sheets 40accommodated in the paper supply hopper 210, and a paper separationmechanism 800 for preventing two or more paper sheets supplied by thepaper supply roller 220 from being fed to the paper transport mechanism300.

The paper supply hopper 210 includes a hopper table 212 supported forpivotal motion on a rotatable shaft 212A located at a rear end portion(right end portion in FIGS. 4 and 7) of the image reading apparatus. Thehopper table 212 is driven at an end portion (left end portion in FIGS.4 and 7) thereof by a rack-and-pinion mechanism 248 (including a pinion248A and a rack 248B) of the paper supply hopper driving mechanism 240so that it is pivoted upwardly and downwardly and adjusted to apredetermined inclined position. The hopper table 212 includes, as shownin FIG. 5, a pair of tiltable paper edge guide members 214 for guidingthe opposite side edges of the paper sheets 40 accommodated in the papersupply hopper 210.

The paper supply hopper driving mechanism 240 includes, as a drivingsource, a hopper motor 242 constituted from a stepper motor. The drivingforce of the hopper motor 242 is transmitted to the rack-and-pinionmechanism 248 by way of a belt-and-pulley mechanism 244.

Meanwhile, the paper supply roller 220 is supported for rocking motionaround an axis of a separation roller 820 by way of a rockable arm 292such that it can be retracted upwardly from a space above the papersupply hopper 210 by a paper supply roller retraction mechanism 270.Such upward retraction of the paper supply roller 220 can be performedartificially. However, in a normal condition wherein no artificial forceis applied to the paper supply roller 220, the paper supply roller 220remains at a position suitably moved down by the weight of the papersupply roller 220 itself or by means of a spring not shown, at which thepaper supply roller 220 is received by the hopper table 212 below. Then,when the paper supply hopper 210 is pivoted, the paper supply roller 220is moved upwardly by a required amount in response to the position ofthe upper face of the paper sheets 40 accommodated in the hopper table212 which is moved upwardly or downwardly by pivotal motion of the papersupply hopper 210.

Referring now to FIGS. 4, 7, 8 and 9, the paper supply roller drivingmechanism 230 for driving the paper supply roller 220 to rotateincludes, as a driving source, a transport motor 342 constituted from astepper motor. The paper supply roller driving mechanism 230 furtherincludes a first belt-and-pulley mechanism 344 and first to third gearmechanisms 852, 856 and 232 interposed between the transport motor 342and the paper supply roller 220. A pick clutch 238 constituted from anelectromagnetic clutch is provided at an inputting portion of thedriving force to the paper supply roller 220 from the third gearmechanism 232.

The paper supply roller driving mechanism 230 is controlled by papersupply roller driving mechanism control means 250 in response to thepaper supplying position (hopper paper supplying position) of the papersupply hopper 210. More particularly, the paper supply roller drivingmechanism control means 250 controls the pick clutch 238 between on andoff states to control operation of the paper supply roller drivingmechanism 230, that is, the rotation condition of the paper supplyroller 220.

The paper separation mechanism 800 includes a separation roller 820, arotation member 830 disposed in an opposing relationship to theseparation roller 820 with a small gap left therebetween, and aseparation roller driving mechanism 850 for driving the separationroller 820 to rotate.

The rotation member 830 is located below the separation roller 820, thatis, nearer to the apparatus body 10 than the separation roller 820, witha small gap left therebetween. The rotation member 830 includes a pairof pulleys 834 and 836 disposed in a spaced relationship from each otherin the paper transporting direction and an endless belt 838 woundbetween and around the pulleys 834 and 836.

The separation roller driving mechanism 850 is constituted fromcomponents substantially common to those of the paper supply rollerdriving mechanism 230 described hereinabove. In particular, as shown inFIGS. 4, 7, 8 and 9, the separation roller driving mechanism 850includes the transport motor 342 described hereinabove as a drivingsource and further includes the first belt-and-pulley mechanism 344 andthe first and second gear mechanisms 852 and 856 interposed between thetransport motor 342 and the paper supply roller 220. A separation clutch854 constituted from an electromagnetic clutch is interposed in thefirst gear mechanism 852. In short, the paper supply roller drivingmechanism 230 has a construction wherein the third gear mechanism 232 isprovided in addition to the separation roller driving mechanism 850. Itis to be noted that operation of the separation clutch 854 is controlledby separation clutch control means 858.

Meanwhile, the paper transport mechanism 300 includes a paper transportpath 310 for transporting a paper sheet 40 supplied thereto from thepaper supply mechanism 200, a plurality of paper transporting rollers320 to 328 disposed along the paper transport path 310, a roller drivingmechanism 340 for driving the paper transporting rollers 320 to 328, androller driving mechanism control means 350 for controlling the rollerdriving mechanism 340. Idler rollers 330 to 338 are providedcorresponding to the paper transporting rollers 320 to 328,respectively.

The paper transport path 310 includes an inclined transport path 312 fortransporting a paper sheet supplied thereto from the paper supplymechanism 200 in an inclined condition, and a paper reversing transportpath 314 provided contiguously to the inclined transport path 312 forreversing the paper sheet 40 transported by the inclined transport path312.

Due to the construction of the paper transport path 310, the posture ofone of the paper sheets 40 supplied from the paper supply hopper 210 ischanged first from a substantially horizontal posture in the papersupply hopper 210 to a rearwardly inclined posture in the inclinedtransport path 312 and is then reversed by the paper reversing transportpath 314, and then, in this posture, the paper sheet 40 is discharged tothe paper stacking mechanism 500.

Consequently, a paper sheet which is directed upwardly in the papersupply hopper 210 is directed downwardly in the paper stacking mechanism500, and the paper sheets 40 accommodated one on another in the papersupply hopper 210 are successively stacked into the paper stackingmechanism 500 without changing the order of them.

Meanwhile, the paper transporting rollers 320 to 328 and the idlerrollers 330 to 338 are disposed in a condition distributed discretely ata distance smaller than the length of the paper sheets 40 in thetransporting direction as seen from FIGS. 4, 7, 8 and 9.

The roller driving mechanism 340 includes the transport motor 342described above as a driving source and further includes a secondbelt-and-pulley mechanism 348 in addition to the first belt-and-pulleymechanism 344. The first and second belt-and-pulley mechanisms 344 and348 will be described here. The first belt-and-pulley mechanism 344includes a pulley 344A mounted on a rotary shaft of the transport motor342, another pulley 344B mounted on a rotary shaft 320A of the papertransporting roller 320, and a belt 346A wound between and around thepulleys 344A and 344B. The second belt-and-pulley mechanism 348 includespulleys 320B to 328B mounted on the rotary shafts 320A to 328A of thepaper transporting rollers 320 to 328, respectively, and a belt 346Bwound between and around the pulleys 320B to 328B.

Accordingly, when the transport motor 342 operates, the driving force istransmitted from the rotary shaft of the transport motor 342 to thepulley 344B by way of the pulley 344A and the belt 346A so that therotary shaft 320A of the paper transporting roller 320 is driven torotate. Further, from the pulley 320B, the rotary shafts 322A to 328A ofthe other paper transporting rollers 322 to 328 are driven to rotate byway of the belt 346A and the pulleys 322B to 328B so that the papertransporting rollers 320 to 328 are driven to rotate simultaneously.

It is to be noted that reference numeral 360 denotes a tension pulley.

The paper transport mechanism 300 described above is schematically shownin FIGS. 10 and 11. Referring to FIGS. 10 and 11, the components areshown such that the paper supply hopper 210 is positioned on the leftside while a paper stacker 510 is positioned on the right side and apaper sheet 40 is transported from the left to the right side reverselyto those in FIGS. 4 to 9 so as to conform to time charts which will behereinafter described.

Referring now to FIG. 12, the optical image reading mechanism 400includes an optical image reading unit 410 having a reading point 422located intermediately of the inclined transport path 312 for opticallyreading information on a paper sheet 40, and image informationextraction control means 440 for controlling extraction of imageinformation read by the optical image reading unit 410.

Referring to FIGS. 4 and 7, the optical image reading unit 410 includes,in the arrangement shown, two units of a first optical image readingunit 412 and a second optical image reading unit 414. The optical imagereading units 412 and 414 are located intermediately of the inclinedtransport path 312, and the first optical image reading unit 412optically reads information on the front face 42 of a paper sheet 40while the second optical image reading unit 414 optically readsinformation on the rear face 44 of the paper sheet 40.

Here, each of the optical image reading units 412 and 414 is constitutedas an image reading unit of common specifications. For example, FIG. 12is a schematic side elevational view showing the construction of theimage reading unit of common specifications. Referring to FIG. 12, theoptical image reading unit 410 shown includes a fluorescent lamp unit420 serving as a lighting element for irradiating light upon the readingpoint 422 on the inclined transport path 312, a CCD (charge coupleddevice) circuit board 436 including a CCD array 436A (CCD array 436Adenotes a plurality of CCDs arranged in an array) for optically readinginformation on a paper sheet 40, and a video circuit board 438 forprocessing information from the CCD array 436A. It is to be noted thatreference numeral 434 in FIG. 12 denotes a black box.

A light path 418 from the reading point 422 to the CCD array 436A isconstituted from a plurality of (in the arrangement shown, three, firstto third) mirrors 418A, 418B and 418C for reflecting light. A shadingplate 430 and a lens 432 are located intermediately of the light path418 between the mirror 418C and the CCD array 436A so that an image fromthe mirror 418C may be introduced into the CCD array 436A by way of thelens 432 after it is corrected, particularly at peripheral portionsthereof, by the shading plate 430.

Since the light path 418 is formed by the plurality of mirrors 418A,418B and 418C for reflection of light, the light path 418 can have asufficient length while the reading point 422 and the CCD circuit board436 are located at comparatively near locations to each other.Consequently, even where the lens 432 has a great focal length, thereading point 422 can be disposed at a focus position of the lens 432.

A paper sheet 40 from which information has been read by the opticalimage reading mechanism 400 in this manner is discharged from the papertransport mechanism 300 to the paper stacking mechanism 500. Here, atthe terminal end of the paper transport mechanism 300, a paper dischargeroller mechanism 540 is located so that the paper sheet 40 may bedischarged to the paper stacking mechanism 500 while being driven by thepaper discharge roller mechanism 540.

The paper stacking mechanism 500 includes a stacker table 520 having, atthe bottom thereof, the paper stacker 510 on which paper sheets 40 canbe stacked. A paper trailing end guide mechanism 550 for guiding therear end 48 of a paper sheet 40 to be stacked into the paper stacker510.

Referring back to FIGS. 4, 7 and 11, several sensors 610 to 618, 620A to620D and 622 are provided. Thus, operations of the driving systemsdescribed above, that is, operations of the hopper motor 242 of thepaper supply hopper driving mechanism 240, the pick clutch 238 of thepaper supply roller driving mechanism 230, the separation clutch 854 andthe roller driving mechanism 340 of the separation roller drivingmechanism 850, and the transport motor 342 for the separation rollerdriving mechanism 850 and the paper supply roller driving mechanism 230and extraction operations of the image information extraction controlmeans 440 of the first optical image reading unit 412 and the secondoptical image reading unit 414 are controlled in response to detectionsignals from the sensors 610 to 618 and 620A to 620D.

The sensor (SHE) 610 is a hopper empty sensor for detecting whether ornot the paper supply hopper 210 is empty. The sensor (SPK) 612 is apaper supply sensor for detecting whether or not the posture of thepaper supply hopper 210 is in an optimum condition (that is, a hopperpaper supplying position) for supplying a paper sheet. Here, since thepaper supply roller 220 is put into a paper supplying position (optimumcondition) in response to the paper supplying position of the papersupply hopper 210, the sensor 612 actually detects whether or not thepaper supply hopper 210 and the paper supply roller 220 are in theirindividual paper supplying positions. The hopper empty sensor 610 andthe paper supply sensor 612 may each be constituted from, for example, aphoto-interrupter.

The sensor (SF1) 614 and the sensor (SF2) 616 are transport sensors fordetecting a paper sheet 40 is transported by the paper transportmechanism 300. The sensor (SF3) 618 is a discharge sensor for detectingwhether or not a paper sheet 40 is discharged from the paper transportmechanism 300 to the paper stacking mechanism 500. The transport sensors614 and 616 and the discharge 618 may each be constituted from, forexample, a photo-sensor. Here, the transport sensor 614 is atransmission type photo-sensor which includes a light emitting elementand a light receiving element located on the opposite sides of the papertransport mechanism 300, and each of the transport sensor 616 and thedischarge sensor 618 is a reflection type sensor wherein a lightemitting element and a light receiving element are provided as a unitarymember.

The sensor (SB5) 620A, the sensor (SA4) 620B, the sensor (SB4) 620C andthe sensor (SA3) 620D are sheet width detection sensors. The sensor 620Ais a B5 width detection sensor provided for detection of a paper widthof a paper sheet of the "B5 size"; the sensor 620B is an A4/LT widthdetection sensor provided for detection of a paper width of a papersheet of the "A4 size" or "LT size"; the sensor 620C is a B4 widthdetection sensor provided for detection of a paper width of a papersheet of the "B4 size"; and the sensor 620D is an A4/DL width sensorprovided for detection of a paper width of a paper sheet of the "A3size" or "DL size". The sensors 620A to 620D may each be constitutedfrom, for example, a photo-sensor (in the arrangement shown, areflection type photo-sensor is employed).

Meanwhile, the sensor 622 is a bottom sensor for discriminating whetheror not the hopper table 212 of the paper supply hopper 210 is at itslowermost position (bottom position). The sensor 622 may be, forexample, a photo-interrupter.

For starting and stopping operations, setting of an operation conditionand so forth of the image reading apparatus described above, anoperation panel 920 is provided at the front of the image readingapparatus as shown, for example, in FIG. 5.

2. Image Reading Mechanism

The optical image reading unit 410 includes, in the arrangement shown,two units of the first optical image reading unit 412 and the secondoptical image reading unit 414 as described hereinabove. The opticalimage reading units 412 and 414 are located intermediately of theinclined transport path 312, and the first optical image reading unit412 optically reads information on the front face 42 of a paper sheet 40while the second optical image reading unit 414 optically readsinformation on the rear face 44 of the paper sheet 40.

As described above, since the optical image reading units 412 and 414are constructed as image reading units of common specifications, whenthere is no necessity of distinguishing them from each other in thedescription of each optical image reading unit, the optical imagereading unit is represented by the optical image reading unit 10. Inparticular, the light path 418 from the reading point 422 to the CCDcircuit board 336 in the optical image reading unit 410 is schematicallyshown in FIG. 13 wherein the light path 418 is generally represented asa straight line omitting the reflections by the mirrors 418A, 418B and418C. Referring to FIG. 13, pieces of image information arranged in thewidthwise direction of a paper sheet 40 are collected by the lens 432and come to the CCD circuit board 436. The CCD circuit board 436 isconstituted from a plurality of CCDs arranged in a juxtaposedrelationship to each other so as to catch the pieces of informationarranged in the widthwise direction.

The shading plate 430 located forwardly of the lens 432 corrects theimage information since the image information is distorted by anincreasing amount toward the opposite left and right ends and of thepaper sheet 40.

The CCD array 436A operates under the control of respective CCD driversto catch image information, and the image information is sent to andprocessed by a video circuit provided on the video circuit board 438.

By the way, in each of the optical image reading units 410, thefluorescent lamp unit 420 is provided in order to make the reading point422 light.

It is to be noted that a heater (not shown) is provided along the rearface of the fluorescent lamp of the fluorescent lamp unit 420. When thetemperature is low, the heater is rendered operative, and after it isstarted, the fluorescent lamp is warmed up rapidly so that the readingpoint 422 can be illuminated with a sufficient amount of light.

3. Read Image Data Processing

3-1. Outline of the Read Image Data Processing System

Referring to FIG. 3, the image reading apparatus includes a first imagedata processing system D1 for processing image data read by the firstoptical image reading unit 412 for reading information on the front faceof a paper sheet, and a second image data processing system D2 forprocessing image data read by the second optical image reading unit 414for reading information on the rear face of the paper sheet.

The first image data processing system D1 includes a CCD array 436AA ofthe first optical image reading unit 412, an amplification circuit (AMP)64A, a sample hold circuit 66A, an analog to digital (A/D conversioncircuit 60A, and an image processing section 68A. Meanwhile, the secondimage data processing system D2 includes a CCD array 436AB of the secondoptical image reading unit 414, an amplification circuit 64B, a samplehold circuit 66B, an analog to digital conversion circuit 60B and animage processing section 68B.

The CCD arrays 436AA and 436AB read image data of a paper sheet by wayof the image reading units 412 and 414, respectively, as describedhereinabove. The amplification circuits 64A and 64B amplify the imagedata of the paper sheet obtained from the CCD arrays 436AA and 436AB,respectively, and the sample hold circuits 66A and 66B sample and holdthe image data of the paper sheet after amplified by the amplificationcircuits 64A and 64B, respectively.

The analog to digital conversion circuits 60A and 60B convert analogdata obtained from the image reading units 412 and 414 into digital datausing white level information and black level information of the imageinformation of the paper sheet as indices for a conversion criterion.The image processing sections 68A and 68B process the digital data fromthe analog to digital conversion circuits 60A and 60B, respectively, byvarious processes such as binary digitization, emphasis and smoothing.

The image data processing system further includes an outputting section90 for selectively sending out paper front face image data and paperrear face image data to a host computer (not shown) in response to aninstruction from an output control circuit 100 which is part of theimage information extraction control means 440. In particular, in thepresent embodiment, since the image reading units 412 and 414 areprovided in the proximity of each other, it sometimes occurs that theimage reading units 412 and 414 read images simultaneously. Therefore,information from the second optical image reading unit 414 for readinginformation on the rear face of a paper sheet is stored once into abuffer storage apparatus (DRAM) of the rear face reading board 944(refer to FIG. 32) and, after information from the first optical imagereading unit 412 is sent to the host computer, the information from thesecond optical image reading unit 414 is sent from the buffer storageapparatus to the host computer. Such control means is provided in theoutputting section 90, and details of the same will be hereinafterdescribed.

In this manner, image information read by the image reading units 412and 414 is read out under the control of the output control circuit 100of the image information extraction control means 440 as seen from FIG.7. In this instance, in the image information extraction control means440, transfer control of image information to the host computer and likecontrol are performed in response to results of detection of a paperleading end detection circuit (paper leading end detection means) 450and a paper trailing end detection circuit (paper trailing end detectionmeans) 451. It is to be noted that the paper leading end detectioncircuit 450 and the paper trailing end detection circuit 451 will behereinafter described.

In particular, the paper leading end detection circuit 450 detects thepaper leading end 46 from a variation of the output of each of theoptical image reading units 410, and the paper trailing end detectioncircuit 451 detects the paper trailing end 48 from a variation of theoutput of each of the optical image reading units 410. The paper leadend detection circuit 450 and the paper trailing end detection circuit451 are both provided in the image information extraction control means.It is to be noted that also the paper leading end detection circuit 450and the paper trailing end detection circuit 451 will be hereinafterdescribed.

Further, the image information extraction control means 440 controlsextraction of image information obtained from the first optical imagereading unit 412 and the second optical image reading unit 414 inresponse to a result of selection by the original selection switch 924Lserving as the paper reading selection means and a discrimination mark(not shown) applied to a paper sheet 40.

In particular, it can be selected by the original selection switch 924Lwhether both face reading should be performed or one face reading shouldbe performed, and the image information extraction control means 440performs reading control in response to a result of the selection by theoriginal selection switch 924L. However, paper sheets which require bothface reading and paper sheets which allow one face reading may possiblybe present in a mixed condition. In this instance, when paper sheetsshould be read in a different manner from other paper sheets in whichthe paper sheets are mixed, a discrimination mark is applied to each ofthe paper sheets so that they may be read in a different manner. Thediscrimination mark is provided for discrimination whether the papersheet should be read by one face reading or by both face reading, and isapplied to a location outside an original reading area such as, forexample, a corner of the leading end of the paper sheet 40 so that itmay be distinguished from image information in the original reading areawhich should originally be read.

Therefore, for example, when one face reading originals are mixed inboth face reading originals, if a discrimination mark which designatesone face reading is applied to each of the one face reading originalsthe quantity of which is smaller than that of the both face readingoriginals and it is selectively set by way of the original selectionswitch 924L that both faces of each paper sheet 40 should usually beread, then image information on both faces of a paper sheet is normallyread by both of the first optical image reading unit 412 and the secondoptical image reading unit 414. However, when a discrimination mark 50is detected, image information only on the front face or the rear faceof the paper sheet 40 is read by the first optical image reading unit412 or the second optical image reading unit 414.

On the contrary, when both face reading originals are mixed in one facereading originals, if a discrimination mark which designates double facereading is applied to each of the double face reading originals thequantity of which is smaller than that of the one face reading originalsand it is selectively set by way of the original selection switch 924Lthat one face of each paper sheet 40 should usually be read, then imageinformation only on the front face or the rear face of a paper sheet isnormally read by the first optical image reading unit 412 or the secondoptical image reading unit 414. However, when a discrimination mark isdetected, image information on the both faces of the paper sheet is readby both of the first optical image reading unit 412 and the secondoptical image reading unit 414.

The image information extraction control means 440 further includesdiscrimination mark image erasure means 460 so that the image of suchdiscrimination mark applied to a paper sheet 40 may be erased and onlyimage information to be read originally may be outputted.

By the way, the apparatus body 10 or the apparatus lid 20 assures anupper mounting space (space for the front face reading unit) 26 and alower mounting space (space for the rear face reading unit) 16 havingsubstantially similar sizes and shapes to each other to allow theoptical image reading units 412 and 414 to be mounted in them,respectively (refer to FIG. 4). In the meantime, the optical imagereading unit 410 is prepared by a plural number having differentspecifications having different performances but having substantiallycommon sizes and profiles.

While, in the image reading apparatus of the present embodiment, thefirst optical image reading unit 412 and the second optical imagereading unit 414 are constructed with common specifications, it is easyto construct the first optical image reading unit 412 and the secondoptical image reading unit 414 so as to have different specificationssuch that, for example, the optical image reading unit for front facereading of the construction described above has higher performances thanthe optical image reading unit for rear face reading of the constructiondescribed above.

Further, each of the optical image reading units 410 includes detectionmeans (front/rear face detection means) 630 which can detect that it isinstalled as a unit for front face reading when it is installed in theupper mounting space 26 but detect that it is installed as a unit forrear face reading when it is installed in the lower mounting space 16.The detection means 630 may be constructed such that, for example, afront surface detection projection (not shown) is provided only in theupper mounting space 26 while a rear face detection projection (notshown) is provided only in the lower mounting space 16, and a front facedetection switch (not shown) which is automatically contacted, when itis installed in the upper mounting space 26, by the front face detectionprojection to switch to an on-state and a rear face detection switch(not shown) which is automatically contacted, when it is installed inthe lower mounting space 16, by the rear face detection projection toswitch to an on-state are provided on each of the optical image readingunits 410.

Information detected by the detection means 630 in this manner is sentto the image information extraction control means 440 and used forextraction control of image information.

The image data processing system shown in FIG. 3 further includes a pairof timing circuits 55A and 55B which define, for example, sample holdingtimings of the sample hold circuits 66A and 66B, respectively.

3-2. White Level Information Used upon Analog to Digital Conversion ofImage Data and Associated Factors

As shown in FIG. 3, each of the analog to digital conversion circuits60A and 60B includes a white level information correction circuit (whitelevel information correction apparatus) 70A or 70B and a black levelsetting circuit 61A or 61B.

The white level information correction circuits 70A and 70B individuallyset white level information to be used as indices for a conversioncriterion of the analog to digital conversion circuits 60A and 60B,respectively, and suitably correct the thus set while level information.The black level setting circuits 61A and 61B individually set blacklevel information to be used as indices for a conversion criterion ofthe analog to digital conversion circuits 60A and 60B, respectively. Itis to be noted that the black level setting circuits 61A and 61B areeach constructed as a sample hold circuit.

The white level information correction circuits 70A and 70B will bedescribed in more detail below. Here, since the white level informationcorrection circuits 70A and 70B have a same construction, referencecharacters to components of the white level information correctioncircuits 70A and 70B are not distinguished between A and B.

In particular, referring to FIG. 14, the white level informationcorrection circuit 70 includes a plurality of (for example, two) memorycircuits 72-1 and 72-2 and registers 73-1 and 73-2, selection circuits75a, 75b, 75c and 75d, a data magnification variation circuit 74, awhite level algorithm circuit 77, and so forth.

The memory circuits 72-1 and 72-2 store a plurality of pieces of whitelevel information (individual pieces of white level informationcorrespond to originals having different ground colors) to be used asindices for a conversion criterion. Write/read control of each of thememory circuits 72-1 and 72-2 is performed in response to an instructionwhich is received from an MPU (microprocessor unit) circuit 150 by anaddress controller 72b by way of an input/output port (I/O port) 72a. Itis to be noted that a RAM (random access memory) may be employed for thememory circuits 72-1 and 72-2.

The registers 73-1 and 73-2 serve as buffer circuits for temporarilystoring the outputs of the memory circuits 72-1 and 72-2, respectively.Each of the selection circuits 75a, 75b, 75c and 75d selectively outputsdesired data to a required output line. For example, a multiplexer isused for the selection circuits 75a, 75b, 75c and 75d.

In particular, the selection circuit 75a selectively outputs data fromthe register 73-1 or 73-2 to the data magnification variation circuit 74side. The selection circuit 75b selectively outputs white levelinformation varied by magnification variation by the data magnificationvariation circuit 74 or white level information from the memory circuit72-1 or 72-2. The selection circuit 75c stores the output of the whitelevel algorithm circuit 77 into and updates a required one of the memorycircuits 72-1 and 72-2. The selection circuit 75d supplies the output ofone of the memory circuits 72-1 and 72-2 to the analog to digitalconversion circuit 60 side by way of a digital to analog conversioncircuit 62 (actually, analog to digital conversion circuits 62A and 62Bare provided in the data processing systems D1 and D2, respectively).

The data magnification variation circuit 74 varies data by magnificationvariation by multiplying white level information from the memory circuit72-1 or 72-2 by a desired coefficient (m: in order to lower the whitelevel, a value between 1 and 0 is selected for m, but in order to raisethe white level, a value higher than 1 is selected for m). For example,a digital multiplier is used for the data magnification variationcircuit 74. Further, the magnification variation coefficient m of thedata magnification variation circuit 74 can be varied by an instructionfrom the MPU circuit 150.

The white level algorithm circuit 77 compares white level informationand data obtained from the optical image reading unit 410 with eachother and corrects the white level information in accordance with aresult of the comparison. Referring to FIG. 15, the white levelalgorithm circuit 77 includes a video signal comparator 77a serving as adigital comparison circuit for comparing digital white level informationselected by the selection circuit 75b and digital data obtained from theoptical image reading unit 410 with each other, and an addition circuit77b serving as a white level information correction circuit forcorrecting the white level information in accordance with a result ofthe comparison by the video signal comparator 77a.

The white level information correction circuit 70 will be described inmore detail.

Referring first to FIG. 14, analog video signals from the CCD arrays436AA and 436AB are amplified by the amplification circuits 64A and 64B,respectively, and, for example, those analog video signals of theoutputs of the amplification circuits 64A and 64B in portions (bits) inwhich photosensitive portions of the CCD arrays 436AA and 436AB aremasked are sampled and held by black level setting circuits (sample holdcircuits) 71A and 71B, respectively. The thus held analog video signalsare connected as reference signals for a black level to the lower limitsides (VRB) of the analog to digital conversion circuits 60A and 60B.Meanwhile, reference signals for a white level are obtained byconverting white level values in lines obtained in the last scanningcycle and stored in the memory circuit 72-1 or 72-2 into analog signalsby means of the digital to analog conversion circuits 62A and 62B, andare connected to the upper limit sides (VRT) of the analog to digitalconversion circuits 60A and 60B, respectively.

Consequently, the analog to digital conversion circuits 60A and 60Boutput digital signals on the scale of 256 gradations between the whitereference level (VRT) and the black reference level (VRB). In thisinstance, for the white reference level, an analog value of a whitelevel produced corresponding to a white level obtained in the lastscanning cycle for an image is used, and for the black reference level,an analog value of a dot at which the photosensitive portion of the CCDarray 436AA or 436AB is masked is used.

By the way, white reference level data extracted from the memory circuit72-1 or 72-2 is fetched into the corresponding register 73-1 or 73-2,and one of the outputs of the registers 73-1 and 73-2 is selected by theselection circuit 75a and then multiplied by m by the data magnificationvariation circuit 74.

Further, the output of the data magnification variation circuit 74 ordata extracted from the memory circuit 72-1 or 72-2 is selected by theselection circuit 75b and inputted to the terminal b of the white levelalgorithm circuit 77.

Meanwhile, a digital value of a video signal which is the output of theanalog to digital conversion circuit 60 is inputted to the otherterminal a of the white level algorithm circuit 77. Consequently, thethus inputted digital value is inputted to comparators (COMP) 77a-0 to77a-2 of the video signal comparator 77a shown in FIG. 15 and thenoutputted from the video signal comparator 77a as one of, for example,three different outputs including X"FF" (white represented by X"FF" bythe 256 gradation representation), X"F7" to X"FE" (a little dark whiterepresented by X"F7" to X"FE" by the 256 gradation representation) andX"F6" or less (white represented by X"F6" or less by the 256 gradationrepresentation).

In the video signal comparator 77a, when the comparators (COMP) 77a-0 to77a-2 detect that the digital output of the analog to digital conversioncircuit 60 is X"FF" mentioned above (that is, when a coincidence outputis obtained), it is recognized that the analog video signal obtained byscanning of the current scanning line of the image is equal to or muchhigher than a white level obtained by scanning in the last scanningcycle, and the white level value of the preceding cycle is incremented,for example, by one.

However, when it is detected that the digital output of the analog todigital conversion circuit 60 falls within the range from X"FE" toX"F7", it is recognized that the analog video signal is a little lowerthan the white level obtained in the last scanning cycle, and the whitelevel value of the last cycle is incremented by, for example, "-1", thatis, decremented by one. Particularly, since no carry need be taken intoconsideration, X"FF", which is a complementary number on 2, should beadded.

When it is detected that the digital output of the analog to digitalconversion circuit 60 is equal to or lower than X"F6", it is recognizedthat not the white level varies but the image now is on the gray leveland is considered that it is not related to correction of the whitelevel, and such control as to perform nothing (particular, to add X"00")is performed to calculate a new white level and determine the new whitelevel as a correction value for scanning of the present scanning line.

When one of the comparators (COMP) 77a-0, 77a-1 and 77a-2 outputs "1",only a corresponding one of gate circuits (DV) 77a-3 to 77a-5 in thevideo signal comparator 77a outputs the value to be added (X"01", X"FF"or X"00" in FIG. 15) while the other gate circuits (DV) exhibit a highimpedance state. For example, when the output is extracted from the gatecircuit 77a-3, the other gate circuits 77a-4 and 77a-5 exhibit a highimpedance state. Thus, the gate circuits 77a-3 to 77a-5 operate astri-state elements.

Then, the output from one of the gate circuits (DV) 77a-3 to 77a-5outputted from the video signal comparator 77a is added to a digitalvalue (W0 to W7 in the last cycle) of the white level of the last cycle,which is the output of the selection circuit 75b, by the additioncircuit 77b. Then, a result of the addition is outputted as a correctionvalue (W0 to W7 in the present cycle) of the white level for the presentscanning cycle from the terminal c of the white level algorithm circuit77 and is stored into the memory circuit 72-1 or 72-2 selected by theselection circuit 75c. It is to be noted that, as shown in FIG. 15, theaddition circuit 77b is constituted from an adder 77b-0 and a flip-flop77b-1 of one stage. The flip-flop (FF) 77b-1 operates as a hazardprevention mechanism when the correction value in the present cycle isadded to the white level corrected in the last scanning cycle and aresult of the addition is stored into the memory circuit 72-1 or 72-2.

Such new white level values based on analog video signals of pictureelements of a line obtained by scanning the image by means of the CCDarray 436A in such a manner as described above are stored into an areaof one of the memory circuits for corresponding picture elements of theline selected by the selection circuit 75d. Then, each time a next lineis read and analog to digital conversion is performed, the white levelvalues are read out as correction values and are each used as the upperlimit value (VRT) for the analog to digital conversion circuit 60 andfurther referred to for correction of the white level of each pictureelement of the line.

Naturally, processing of scanning a certain line of the image by meansof the CCD array 436A and reading out analog video signals of theindividual picture elements and processing of reading out values ofwhite levels of a line scanned in the last scanning cycle from thememory circuit 72-1 or 72-1 are synchronized with a shift pulse signalused to scan the image by means of the CCD array 436A, and the addressin the scanning line and the address of the memory circuit 72-1 or 72-2described hereinabove (the address of the memory circuit of the 8 Kwordcapacity) are synchronized with each other with an offset of oneaddress.

Further, in the white level information correction circuit 70, forexample, in such a case that paper sheets whose ground color is whitehave been read till now and blue print paper sheets of a differentground color are to be read subsequently, the white level value to beprovided to the analog to digital conversion circuit 60A or 60B isvaried in response to an instruction signal from the MPU circuit 150when a manual instruction or an automatic instruction is provided to theMPU circuit 150. To this end, white level information stored in thememory circuit 72-1 (or 72-2) is taken out and stored into the register73-1 (or 73-2), and then the output of the register 73-1 is selected bythe selection circuit 75a so that it is subsequently multiplied by m bythe data magnification variation circuit 74. The magnification variationfactor m can be modified freely in response to an instruction from theMPU circuit 150. This increases the degree of freedom in correction of awhite level.

Then, the output of the data magnification variation circuit 74 isselected by the selection circuit 75b and then processed by requiredprocessing by the white level algorithm circuit 77, and then the whitelevel of the thus varied magnification is stored into the other memorycircuit 72-2 (or 72-1) by way of the selection circuit 75c. Then, thewhite level of the varied magnification is used as a conversionreference of the analog to digital conversion circuit 60.

It is to be noted that signals at several locations of the circuitryshown in FIG. 14 in this instance (locations denoted at (1) to (8) inFIG. 14, and the output enable signal OE and the write enable signal WEfor a memory circuit) are illustrated in the time chart of FIG. 18.

Thereafter, so far as such blue print paper sheets are used, white levelinformation from the memory circuit 72-2 (or 72-1) in which data of thewhite level information multiplied by m is stored is extracted, and now,the output of the memory circuit 72-2 (or 72-1) is inputted by way ofthe selection circuit 75b to the white level algorithm circuit 77, bywhich the processing described above is performed subsequently so thatthe white level value may have an appropriate value to update the whitelevel.

Consequently, even in such a case that paper sheets whose ground coloris white have been read till now and blue print paper sheets of adifferent ground color are to be read subsequently, the white levelinformation correction apparatus copes with this sufficiently and canperform analog to digital conversion with a high degree of accuracy.Besides, by constructing the correction circuit for a white level from adigital circuit, analog parts in the entire circuit and patterns of aprinted circuit board of an image inputting device can be reduced to theminimum. Further, since correction of a white level is performed bydigital processing, no oscillation occurs in a high frequency bandwhereas it occurs often with an analog comparator. Accordingly, also theadvantage that an increase in stability of operation and in efficiencyand certainty in designing can be achieved is obtained.

Further, the white level algorithm circuit 77 may include, as shown inFIG. 16, a video signal comparator 77c serving as a control signalgeneration circuit for comparing digital white level informationselected by the selection circuit 75b and digital data obtained from theoptical image reading unit 410 with each other and outputting, inaccordance with a result of the comparison, a control signalrepresenting that the digital data is a predetermined value, a countingsection (counting circuit) 77d for counting the number of times by whicha control signal is successively outputted in the direction of a linefrom the video signal comparator 77c, an addition value selectingmultiplexer 77e serving as a white level information correction circuitfor correcting white level information in accordance with a countedvalue of the counting section 77d, and an addition circuit 77f.

In particular, also in this instance, a digital signal from the analogto digital conversion circuit 60 is inputted to comparators (COMP) 77c-0to 77c-2 in the video signal comparator 77c, by which it is divided, forexample, into three different outputs (X"FF", X"F7" to X"FE", and X"F6"or less) by similar operation to that described hereinabove withreference to FIG. 15.

The outputs of the comparators (COMP) 77c-0 to 77c-2 in the video signalcomparator 77c in this instance are outputted by way of gate circuits(G) 77c-3 to 77c-5 and inputted to the counting section (Count) 77d asseen from FIG. 16.

In this instance, each of the memory circuits 72-1 and 72-2 storesinformation of 8 bits (W0 to W7) necessary to store digital values ofwhite levels of ordinary picture elements obtained by scanning in thelast scanning cycle. The 8 bits mentioned above are a new white levelsignal to be used for a next line which has been produced from a digitalvalue outputted from the analog to digital conversion circuit 60described hereinabove and an upper limit signal used thereupon by theanalog to digital conversion circuit 60. Each of the memory circuits72-1 and 72-2 further stores, for example, the output of four bits (Qato Qd) of the counting section (Count) 77d corresponding to each bit ofthe line.

The output signal of the comparator (COMP) (=FF?) 77c-0 mentioned aboveis connected to a count enable (EN) terminal of the counting section(Count) 77d, and the four bits (Qa to Qd) of the count value for eachpicture element obtained by scanning in the last scanning cycle andstored in the memory circuit 72-1 or 72-2 are inputted to terminals Dato Dd of the counting section (Count) 77d. While the count value (Da toDd) is inputted, when the output of the analog to digital conversioncircuit 60A or 60B in the present scanning cycle is X"FF" andconsequently a coincidence signal is outputted from the comparator(COMP) (=FF?) 77c-0 so that the count enable (EN) terminal of thecounting section (Count) 77d is energized, the counting section (Count)77d counts up the input value (Da to Dd). However, when the count enable(EN) terminal is not energized and the output signal of one of the othercomparators (COMP) (=F7 to FE?, -F6?) 77c-1 and 77c-2, the resetterminal (RST0 or RST1) of the counting section (Count) 77d is energizedso that the count value (Da to Dd) for each picture element is cleared.

In particular, in the counting section (Count) 77d, the count value (Qato Qd) in the last scanning line for each dot of the CCD array 436A isread out from a corresponding address of the memory circuit 72-1 or 72-2in synchronism with a shift pulse for shifting the CCD array 436A and isloaded to the Da to Dd terminals of the counting section (Count) 77c sothat X"FF" which represents a white level is counted for each dot todetermine by what number of success lines X"FF" appears. When thedigitally converted value of the dot falls within the range of X"F7" toX"FE" or X"F6" or less, the count value for the dot loaded to the Da toDd terminals of the counting section (Count) 77d is cleared.

In the addition value selecting multiplexer (correction value conversioncircuit) 77e shown in FIG. 16, one of gate circuits (DV) 77e-0 to 77e-4is selected in response to a signal obtained from a decoder (DEC) 77g bydecoding an output value of the counting section (Count) 77d and signalsα, β and γ(τ) outputted from the comparators (COMP) 77c-0, 77c-1 and77c-2 of the video signal comparator 77c by way of the gate circuits (G)77c-3, 77c-4 and 77c-5, respectively, to select an addition value(X"01", "X02" or X"04") to be added to a white level of each pictureelement of a line obtained by the line scanning in the last scanningcycle and stored in the memory circuit 72-1 or 72-2.

The decoded signal from the decoder 77g is "01" when the count value ofthe counting section 77d is "1", that is, when the count value signifiesthat the white level corrected in the last scanning cycle is not X"FF"but the white level in the present scanning cycle is X"FF"; the decodedsignal is "02" when the count value is "02", that is, when the countvalue signifies that the white level corrected in the last scanningcycle is X"FF" and also the white level in the present scanning cycle isX"FF"; and the decoded signal is "03" when the count value is "03", thatis, when the count value signifies that the white level corrected in thesecond last scanning cycle is X"FF" and also the white level correctedin the last scanning cycle is X"FF" and besides also the white level inthe present scanning cycle is X"FF".

Accordingly, when the count value (Qa to Qd) of the counting section(Count) 77d is, for example, "01", it is recognized that the correctedwhite level value in the last scanning cycle was not X"FF", and the gatecircuit (DV) 77e-2 of the addition value selecting multiplexer 77e isselected. Consequently, the input α to the gate circuit (G) 77e-2 isenergized to determine "+1" as the correction value for the white levelvalue of the last scanning cycle so that the correction value "+1" maybe added by the addition circuit 77f.

Similarly, when the count value (Qa to Qd) of the counting section(Count) 77d is, for example, "02", it is recognized that the correctedwhite level value in the last scanning cycle was X"FF" and then thewhite level of the dot in the present scanning cycle is X"FF", and thegate circuit (DV) 77e-3 is selected. Consequently, the input α to thegate circuit (C) 77e-3 is energized to determine "+2" as the correctionvalue for the white level value of the last scanning cycle.

Further, similarly, when the count value (Qa to Qd) of the countingsection (Count) 77d is, for example, equal to or higher than "03", it isrecognized that the successive corrected white level values in the lastscanning cycle and the second last scanning cycle were X"FF" and thenalso the white level of the dot in the present scanning cycle is X"FF",and the gate circuit (DV) 77e-4 is selected. Consequently, the input αto the gate circuit (G) 77e-4 is energized to determine "+4" as thecorrection value for the white level value of the last scanning cycle.

In any other instance, depending upon whether an output is outputtedfrom the comparator (=F7 to FE?) 77c-1 or the comparator (-F6?) 77c-2 ofthe video signal comparator 77c, the corresponding gate circuit (DV)77e-0 or 77e-1 is selected so that the input β or γ(τ) of the gatecircuit (G) 77e-1 or 77e-0 is energized. Consequently, same correctionas that described hereinabove with reference to FIG. 15 is performed.

In particular, the control method in the present example described aboveis characterized in that, when X"FF" as a white level successivelyappears in successive lines at a certain dot, it is recognized that asudden variation in white has occurred and thus such a correction isperformed that the white level value is raised progressively inaccordance with such sudden variation in white.

FIG. 17 shows a modification to the white level algorithm circuit 77shown in FIG. 16. In particular, referring to FIG. 17, the modifiedwhite level algorithm circuit 77 includes, for example, a read-onlymemory (ROM) 77h in place of the addition value selecting multiplexer77e and the addition circuit 77f of the white level algorithm circuit 77shown in FIG. 16. In particular, the output value (4 bits) of thecounting section (Count) 77d, the output (3 bits) of the video signalcomparator 77c and a white level value (8 bits) in the memory circuit72-1 or 72-2 obtained by scanning in the last scanning cycle are appliedas an address signal to the ROM 77h so that a white level valuecalculated and stored in advance in the ROM 77h is outputted from theROM 77h.

The white level value outputted in this manner is stored into theposition corresponding to the dot together with the value (Qa to Qd) ofthe counting section (Count) 77d and then used for calculation for whitelevel correction upon analog to digital conversion in a next line.

Then, also in this instance (in the case of FIGS. 16 or 17), in such acase that paper sheets whose ground color is white have been read tillnow and blue print paper sheets of a different ground color are to beread subsequently, the white level value to be provided to the analog todigital conversion circuit 60 is varied in response to an instructionsignal from the MPU circuit 150 by the white level informationcorrection circuit 70 in a similar manner as described above. Inparticular, white level information stored in the memory circuit 72-1(or 72-2) is taken out and stored into the register 73-1 (or 73-2), andthen the output of the register 73-1 (or 73-2) is selected by theselection circuit 75a so that it is subsequently multiplied by m by thedata magnification variation circuit 74. Then, the output of the datamagnification variation circuit 74 is selected by the selection circuit75b and then processed by required processing by the white levelalgorithm circuit 77, and then the white level of the thus variedmagnification is stored into the other memory circuit 72-2 (or 72-1) byway of the selection circuit 75c. Then, the white level of the variedmagnification is used as a conversion reference of the analog to digitalconversion circuit 60.

Thereafter, so far as such blue print paper sheets are used, the whitelevel from the memory circuit 72-2 (or 72-1) is extracted, and now, theoutput of the memory circuit 72-2 (or 72-1) is inputted by way of theselection circuit 75b to the white level algorithm circuit 77. Then, theprocessing described above is performed subsequently by the white levelalgorithm circuit 77 shown in FIGS. 16 or 17 so that the white levelvalue may have an appropriate value to update the white level.

Consequently, even in such a case that paper sheets whose ground coloris white have been read till now and blue print paper sheets of adifferent ground color are to be read subsequently, the white levelinformation correction apparatus copes with this sufficiently and canperform analog to digital conversion with a high degree of accuracy.Besides, by constructing the correction circuit for a white level from adigital circuit, analog parts in the entire circuit and patterns of aprinted circuit board of an image inputting device can be reduced to theminimum. Further, since correction of a white level is performed bydigital processing, no oscillation occurs in a high frequency bandwhereas it often occurs with an analog comparator. Accordingly, also theadvantage that an increase in stability of operation and in efficiencyand certainty in designing can be achieved is obtained.

Further, in the case described above, since the digital circuit portionof the white level algorithm circuit 77 can be constructed only fromordinary logical OR and AND gate circuits, it can be included readilyinto a large scale integrated circuit (LSI).

Further, in the arrangement shown in FIG. 17, since the addition valueselecting multiplexer 77e and the addition circuit 77f describedhereinabove with reference to FIG. 15 are replaced, for example, withthe ROM 77h, the number of parts can be reduced, and higher densitymounting can be anticipated.

By the way, in the arrangement shown in FIG. 14, the plurality of (two)memory circuits 72-1 and 72-2 are used in order to store white levelinformation, and the memory circuits 72-1 and 72-2 are selectively usedusing a chip selection function of the address controller 72b. However,such an alternative arrangement as shown in FIG. 19 may be employedwherein a single memory circuit 72 is employed and an address of thememory circuit 72 is designated by the address controller 72b so as toselectively use a pair of different storage areas 72-11 and 72-12 of thememory circuit 72.

Also in this instance, for example, in such a case that paper sheetswhose ground color is white have been read till now and blue print papersheets of a different ground color are to be read subsequently, thewhite level value to be provided to the analog to digital conversioncircuit 60 is varied by the white level information correction circuit70 shown in FIG. 19 in a similar manner as described above. Inparticular, white level information stored in a certain storage area72-11 (or 72-12) of the memory circuit 72 is taken out and stored intothe register 73, and then the output of the register 73 is subsequentlymultiplied by m by the data magnification variation circuit 74. Then,the output of the data magnification variation circuit 74 is selected bythe selection circuit 75b and then processed by required processing bythe white level algorithm circuit 77 (refer to FIGS. 15 to 17), and thenthe white level of the thus varied magnification is stored into theother storage area 72-12 (or 72-11). Then, the white level of the thusvaried magnification is used as a conversion reference of the analog todigital conversion circuit 60.

Thereafter, so far as such blue print paper sheets are used, white levelinformation from the storage area 72-12 (or 72-11) is extracted, andnow, the output of the storage area 72-12 (or 72-11) is inputted by wayof the selection circuit 75b to the white level algorithm circuit 77.Then, the processing described above is performed subsequently by thewhite level algorithm circuit 77 shown in FIGS. 15 to 17 so that thewhite level value may have an appropriate value to update the whitelevel.

In this manner, also in this instance, the effects or advantagesachieved by the embodiment described above can be achieved. Further,since the single memory circuit 72 is employed and the storage area72-11 and 72-12 of the memory circuit 72 are selectively used bydesignating the address by means of the address controller 72b, there isno necessity any more of preparing a plurality of independent memorycircuits. Consequently, handling of the white level informationcorrection circuit 70 is facilitated.

Such another alternative arrangement as shown in FIG. 20 may be employedwherein a switching control circuit 78 is additionally provided forautomatically controlling selective switching of the selection circuit75b in accordance with a result of determination which is conducted bythe data magnification variation circuit 74 based on data obtained fromthe optical image reading unit 410 to determine whether white levelinformation should be varied by magnification variation.

In particular, the switching control circuit 78 includes a pair ofcomparators 78a and 78c and a counter 78b. In the switching controlcircuit 78, the output of the analog to digital conversion circuit 60 isfirst compared with a reference value from reference value setting means78d by the comparator 78a, and if the output of the analog to digitalconversion circuit 60 is higher than the reference value, the counter78b counts up by one. Further, the output of the counter 78b is comparedwith a dot reference value from dot reference value setting means 78e bythe comparator 78c. If the output of the analog to digital conversioncircuit 60 is higher by more than a predetermined line number than thereference value, then since the output of the counter 78b is higher thanthe dot reference value, a signal to instruct the selection circuit 75bto select the data magnification variation circuit 74 is developed fromthe comparator 78c. In response to the signal, the selection circuit 75bselects the output of the data magnification variation circuit 74, andconsequently, the white level is varied more suddenly than that byvariation by the white level algorithm circuit 77. Then, the variationis performed automatically based on data obtained from the optical imagereading unit 410 as described above. It is to be noted that, when theoutput of the analog to digital conversion circuit 60 is still higher bymore than the predetermined line number than the reference value evenafter the selection circuit 75b is switched to the data magnificationvariation circuit 74 side, the white level varied once is further variedby the data magnification variation circuit 74. In particular, if thewhite level is varied, for example, twice, then the white level isvaried to m² times.

It is to be noted that, in FIG. 20, a selection circuit 75e is furtherprovided. The selection circuit 75e selects the output of the whitelevel algorithm circuit 77 or predetermined value data (X"FF" whichcorresponds to the maximum value). In particular, a control signal VABSis supplied from the MPU circuit 150 to the selection circuit 75e sothat, in an initial state, the predetermined value data is outputtedfrom the selection circuit 75e, and thereafter, the output of the whitelevel algorithm circuit 77 is outputted from the selection circuit 75e.

In this manner, also with the white level information correction circuit70 shown in FIG. 20, the effects or advantages which can be achieved bythe embodiment described above can be achieved. Further, since it isdetermined by the data magnification variation circuit 74 based on dataobtained from the optical image reading unit 410 whether or not whitelevel information should be varied by magnification variation and thenselective switching of the selection circuit 75b is automaticallycontrolled in accordance with a result of the determination, even whenpaper sheets used are changed, the white level can be automaticallyvaried rapidly.

It is to be noted that, while, in the several arrangements describedabove, the white level is varied for each picture element, it need notnecessarily be corrected for each picture element, but may naturally becorrected, for example, for each line.

Referring back to FIG. 3, an image signal after digital conversion bythe analog to digital conversion circuit 60 is transferred to the imageprocessing section 68A or 68B for next image processing such as, forexample, emphasis processing to emphasize the contrast between white andblack or "dither processing: binary digitization processing" for a netpoint image (which is constituted from a large number of fine dots; dotimage) such as a photograph image.

3-3. Outputting Section and Output Control Circuit

In each of the image data processing systems D1 and D2, informationdigitized by the analog to digital conversion circuit 60A or 60B issent, after it is processed by emphasis processing and/or binarydigitization processing by the image processing section 68A or 68B, tothe outputting section 90 as seen from FIG. 3, and paper front face dataand paper rear face data are transferred from the outputting section 90to the host computer (not shown).

Referring now to FIG. 21, the outputting section 90 includes a latchcircuit 91, a DRAM (buffer storage apparatus) 92, a rear face memorycontrol section 93, a read data buffer 94, a rear face timing generationsection 95 and a selection circuit 96.

The latch circuit 91 latches paper front face data VDA and front facetiming signals VGA, HGA and VCLKA from the image data processing systemD1 for processing paper front face data and notifies to the outputcontrol circuit 100 that the paper front face data and the surfacetiming signals have been latched by the latch circuit 91. It is to benoted that a flip-flop may be used for the latch circuit 91.

The timing signal VGA is a gate signal in a horizontal direction(direction of a line; main scanning direction), and the timing signalHGA is a gate signal in a vertical direction (paper transportingdirection; sub-scanning direction). One bit of a picture element in oneline on the front face of a paper sheet can be extracted using thetiming signal VGA and the timing signal HGA. Further, the timing signalVCLKA is a clock signal which defines the transfer rate of front facedata.

The DRAM 92 is a memory circuit for storing paper rear face data VDB.Storage and read-out control of the DRAM 92 is performed by the rearface memory control section 93. In particular, the rear face memorycontrol section 93 is constructed as a DMAC (dynamic memory accesscontroller) and stores paper rear face data VDB sent thereto into theDRAM 92. After paper front face data VDA for one sheet are sent, therear face memory control section 93 controls the DRAM 92 so that,between successive storing operations of paper rear face data VDB intothe DRAM 92, the paper rear face data VDB are read out from the DRAM 92(in this instance, the paper rear face data VDB are read out in units ofone bit).

It is to be noted that all data for one full paper sheet from the lateroperating image reading unit 414 need not necessarily be stored into theDRAM 92, and actually, those data obtained after outputting of data forone full paper sheet from the first operating image reading unit 412 iscompleted until all information stored in the DRAM 92 is sent out arestored. In particular, data from the later operating image reading unitare stored for a period of time after outputting of data for one fullpaper sheet from the other first operating image reading unit iscompleted until it becomes possible to pass and output data from thelater operating image reading unit through and from the rear face memorycontrol section 93. This can decrease the memory capacity.

It is a matter of course that data from the later operating imagereading unit 414 may all be stored for one full paper sheet into theDRAM 92. This facilitates memory control.

The read data buffer 94 temporarily stores, between successive storingoperations of paper rear face data VDB into the DRAM 92, paper rear facedata VDB partially read out from the DRAM 92 and produces arranged datato be sent. Where the read data buffer 94 is provided in this manner,data can be read out little from the DRAM 92 while giving priority towriting into the DRAM, and consequently, the data transfer time can bereduced.

It is to be noted that the rate at which data are read out from the DRAM92 and the read data buffer 94 is set equal to twice the writing rate,that is, the transfer rate of front face data to the host computer.

The rear face timing generation section 95 generates rear face timingsignals VGB, HGB and VCLKB. Also in this instance, the timing signal VGBis a gate signal in a horizontal direction (direction of a line; mainscanning direction), and the timing signal HGB is a gate signal in avertical direction (paper transporting direction; sub-scanningdirection). One bit of a picture element in one line on the rear face ofa paper sheet can be extracted using the timing signal VGB and thetiming signal HGB. Further, the timing signal VCLKB is a clock signalwhich defines the transfer rate of front face data. In this instance,the rate of the rear face timing signal VCLKB is set to twice that ofthe front face timing signal VCLKA. Due to the rate and also due to thedata read-out data rate from the DRAM 92 and the read data buffer 94,rear face data are transferred at the rate equal to twice that of frontface data.

The selection circuit 96 receives a control signal from the outputcontrol circuit 100 and selectively outputs paper front face data orpaper rear face data in accordance with the control signal. In thisinstance, after paper front face data are transferred for one full papersheet, the data to be outputted are switched so that paper rear facedata are thereafter transferred for one complete paper sheet.

It is to be noted that the output control circuit 100 is switched to thepaper front face data side in response to paper leading end detectioninformation but is switched to the paper rear face data side in responseto paper trailing end detection information. Such detection of a leadingend or a trailing end of a paper sheet will be hereinafter afterdescribed.

Therefore, it is considered that the outputting section 90 includes thestorage means (DRAM) 92 for storing data (paper rear face data) fromthat one of the first optical image reading unit 412 and the secondoptical image reading unit 414 which serves as a later operating imagereading unit (in the present example, the second optical image readingunit 414) from which paper image information is read out later than fromthe other image reading unit.

Also it is considered that the outputting section 90 further includesfirst data transfer means (the latch circuit 91 and the selectioncircuit 96) for successively transferring, by way of a data transferline, paper front face data from that one of the first optical imagereading unit 412 and the second optical image reading unit 414 whichserves as a first operating image reading unit (in the present example,the first operating image reading unit 412) from which paper imageinformation is read out first, and second data transfer means (the rearface memory control section 93, the rear face timing generation section95 and the selection circuit 96) for successively transferring, by wayof another data transfer line, after paper front face data from thefirst operating image reading unit 412 are transferred by the first datatransfer means, paper rear face data from the later operating imagereading unit 414 stored in the storage means 92 at a rate (in thepresent example, at the twice rate) higher than the data transfer rateby the first data transfer means.

Further, it is also considered that the outputting section 90 furtherincludes auxiliary storage means (the read data buffer 94) for storingpartial paper image information read out from the storage means 92between successive writing operations of data into the storage means(DRAM) 92.

It is to be noted that the reason why paper rear face data are sent at arate twice that of paper front face data is that it is desired thatpaper rear face data be transferred to the host computer side before thepaper sheet 40 whose front face and rear face have been read isthereafter discharged to the stacking mechanism 500. This is because, ifa paper sheet is discharged to the stacking mechanism 500, thentransportation of a new paper sheet is started and reading of data ofthe paper sheet is started. In other words, paper rear face data aretransferred at the rate twice that of paper front face data because itis desired to complete transfer of rear face data before transportationof a next paper sheet is started. Accordingly, naturally the value twicemay possibly be varied depending upon the length of the paper transportpath, the paper transport velocity or the like of the image readingapparatus.

Accordingly, the outputting section 90 operates in such a manner asillustrated in FIG. 22.

Referring to FIG. 22, since the selection circuit 96 is initiallyswitched to the paper front face data side, paper front face data aretransferred by through-transfer (step A1). Thereafter, when the signalVGA becomes negated, that is, when transfer of the front face data iscompleted, the route of "YES" is taken at step A2, and then theselection circuit 96 is switched to the paper rear face data side (stepA3). Then, at step A4, paper rear face data are read out from the DRAM92 and transferred at a high rate to the read data buffer 94 (step A5).Then, this operation is repeated until the DRAM (image sensor) 92becomes emptied (step A6).

Due to the construction described above, data (paper front face data)from the first operating image reading unit 412 from one of the firstoptical image reading unit 412 and the second optical image reading unit414 from which paper image information is to be read out first are firsttransferred successively by way of a data transfer line, and data (paperrear face data) from the later operating image reading unit 414 from oneof the first optical image reading unit 412 and the second optical imagereading unit 414 from which paper image information is to be read outlater are temporarily stored into the DRAM 92 and, after the data fromthe first operating image reading unit 412 are transferred completely,the stored data from the later operating image reading unit 414 aresuccessively transferred at a rate higher than the transfer rate of thedata from the first operating image reading unit 412 by way of anotherdata transfer line. Consequently, the following advantages can beobtained.

In particular, even if image reading by the later operating imagereading unit 414 is started before image reading by the first operatingimage reading unit 412 is completed, data within the overlapping periodcan be held with certainty. Besides, data from the later operating imagereading unit 414 from which data are transferred later can betransferred rapidly to the host computer side.

Accordingly, even where the image reading units 412 and 414 are disposedin the proximity of the paper transport path in order to achieveminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of a paper sheet can be transferred to thehost computer side before the paper sheet is discharged to the stackingmechanism 500. Consequently, even if paper sheets are successivelytransferred at a high speed while achieving minimization, reduction inweight and compaction of the apparatus, data of the front and rear facesof each paper can be read and transferred to the host computer sidesatisfactorily.

By the way, the output control circuit 100 includes, as describedhereinabove, the paper leading end detection circuit 450 for detectingpaper leading end information and the paper trailing end detectioncircuit 451 for detecting paper trailing end information.

The paper leading end detection circuit 450 and the paper trailing enddetection circuit 451 have a same circuit construction and eachincludes, as shown in FIG. 23, magnitude comparators 131, 138 and 139, amultiplexer 132, registers 133, 134, 135 and 141, adders 136 and 137,and an OR gate 140.

Due to the construction, a video signal (paper front face data) from theimage reading unit 412 is inputted to an input terminal A of themagnitude comparator 131. The magnitude comparator 131 thus compares thevideo signal from the image reading unit 412 with the output of theregister 133 which is inputted to the magnitude comparator 131 by way ofanother input terminal B. In this instance, if the video signal ishigher, then the video signal is outputted from the multiplexer 132 sothat it is latched by the register 133. On the contrary if the output ofthe register 133 is higher, then the output of the register 133 isoutputted from the multiplexer 132 so that it is latched by the register133. Such comparison in magnitude is repeated. Consequently, at the endof the line, a maximum value (peak value) of the line is latched in theregister 133.

Therefore, it can be understood that the magnitude comparator 131, themultiplexer 132 and the register 133 construct one-line peak valuedetection means for detecting a peak value in one line along thedirection perpendicular to the paper transporting direction based on animage signal from an optical image reading unit.

Further, a clock BB (this clock BB is developed once for one line at theend of the line) causes the register 134 to latch a maximum value (peakvalue) in one line latched in the register 133 and simultaneously causesthe register 135 to latch a maximum value (peak value) of the last line.Consequently, the registers 133 and 134 construct a shift register forstoring both of a current peak value detected by the one-line peak valuedetection value and a past peak value in one line detected prior to thecurrent peak value.

Meanwhile, the register 135 is constructed as storage means for storinga past peak value in one line detected prior to a current peak valuedetected by the one-line peak value detection means.

Thereafter, +n (n is a natural number) is added to a maximum value (peakvalue) of a preceding line by the adder 136, and -n is added to (thatis, n is subtracted from) the maximum value by the adder 137. Then, theoutput of the adder 136 and the maximum value (peak value) of thecurrent line from the register 134 are compared with each other by themagnitude comparator 138, and the output of the adder 137 and themaximum value (peak value) of the current value from the register 134are compared with each other by the magnitude comparator 139.

Then, if the maximum value of the current line is higher than the sum ofthe maximum value of the preceding line and n, the magnitude comparator138 outputs "1", but if the maximum value of the current line is lowerthan the difference of n from the maximum value of the preceding line,the magnitude comparator 139 outputs "1". Consequently, if the maximumvalue of the current line is higher than the sum of the maximum value ofthe preceding line and n or lower than the difference of n from themaximum value of the preceding line, then the OR gate 140 outputs "1".

Then, the output of the OR gate 140 is latched by the register 141 whichoperates in response to a clock AA (the clock AA is outputted once forone dot) in order to prevent fluctuation, and the output of the register141 is used as a paper leading end detection signal or a paper trailingend detection signal. Then, such paper leading or trailing end detectionsignal is used as an interruption requesting signal (IRQ) to the MPUcircuit 150.

Consequently, it can be seen that the magnitude comparators 138 and 139cooperatively construct comparison means for comparing a current peakvalue detected by the one-line peak value detection means and a pastpeak value from the storage means with each other and outputting aresult of the comparison as a paper leading or trailing end detectionsignal.

Meanwhile, the adder 136 constructs addition means for adding apredetermined value (n) to a past peak value from the register (storagemeans) 135. Thus, the magnitude comparator (comparison means) 138 isconstructed so as to compare a current peak value detected by theone-line peak value detection means and an addition correction past peakvalue from the adder 136 with each other and output a result of thecomparison as a paper end detection signal.

Further, the adder 137 constructs subtraction means for subtracting apredetermined value (n) from a past peak value from the register(storage means) 135. Thus, the magnitude comparator (comparison means)139 is constructed so as to compare a current peak value detected by theone-line peak value detection means and a subtraction correction pastpeak value from the adder 137 with each other and output a result of thesubtraction as a paper leading or trailing end detection signal.

Meanwhile, the magnitude comparator 138 constructs first comparisonmeans for comparing a current peak value detected by the one-line peakvalue detection means and an addition correction past peak value fromthe adder (addition means) 136 with each other. The magnitude comparator139 constructs second comparison means for comparing a current peakvalue detected by the one-line peak value detection means and asubtraction correction past peak value from the adder (subtractionmeans) 137 with each other. The OR gate 140 constructs outputting meansfor outputting, when a paper end detection signal is outputted from atleast one of the first comparison means and the second comparison means,the paper end detection signal as a paper end detection signal.

Further, the register 141 constructs latching means for latching theoutputs of the comparison means.

It is to be noted that FIG. 24 illustrates signal waveforms (time chart)at several locations of the circuit shown in FIG. 23.

The leading end or the trailing end of a paper sheet is detected in sucha manner as described above. The paper leading end detection circuit 450detects the leading end of a paper sheet based on a paper end detectedfor the first time, and when the MPU circuit 150 receives such paperleading end detection signal as an interruption requesting (IRQ) signalfrom the paper leading end detection circuit 450, the MPU circuit 150develops, in response to the interruption requesting (IRQ) signal, acommand signal to read the front face of the paper sheet. As a result,also the selection circuit 96 is switched to the paper front face dataside.

Meanwhile, the paper trailing end detection circuit 451 detects thetrailing end of the paper sheet based on a paper end detected for thesecond time, and when the MPU circuit 150 receives such paper trailingend detection signal as an interruption requesting (IRQ) signal from thepaper trailing end detection circuit 451, the MPU circuit 150 develops,in response to the interruption requesting (IRQ) signal, a commandsignal to read the rear face of the paper sheet. As a result, also theselection circuit 96 is switched to the paper rear face data side.

Therefore, the outputting section 90 is constructed as image signalprocessing means for processing image signals obtained by the opticalimage reading units in response to a result of detection by the paperend detection apparatus.

Accordingly, if the paper leading end detection circuit 450 and thepaper trailing end detection circuit 451 of such circuit construction asdescribed above are employed, the the leading end and the trailing endof a paper sheet can be detected with certainty with a common circuitconstruction and with a simple construction. Consequently, readingtimings of paper front face data and paper rear face data or readingswitching timings between them can be controlled precisely irrespectiveof the type of a paper sheet being transported. As a result, it iscomparatively simple for the image reading apparatus to allow papersheets of various sizes to be transported to read information on them.

It is to be noted that, while any of the leading end and the trailingend of a paper sheet can be detected by the construction shown in FIG.23, where the ground color of a paper sheet 40 is brighter than thecolor of the backing member provided on the paper transport path 310, ifit is intended to only detect the leading end of the paper sheet 40,then the adder 137, the magnitude comparator 139 and the OR gate 140 canbe omitted. Similarly, if it is intended to only detect the trailing endof the paper sheet 40, then the adder 136, the magnitude comparator 138and the OR gate 140 can be omitted. On the contrary, where the groundcolor of a paper sheet 40 is darker than the color of the backing memberprovided on the paper transport path 310, if it is intended to onlydetect the leading end of the paper sheet 40, then the adder 136, themagnitude comparator 138 and the OR gate 140 can be omitted. Similarly,if it is intended to detect only the trailing end of the paper sheet 40,then the adder 137, the magnitude comparator 139 and the OR gate 140 canbe omitted.

4. Control System

4-1. Operation Panel

Referring now to FIG. 31, the operation panel 920 has provided thereonvarious indication lamps including a power source input indication lamp922A, a reading enable indication lamp 922B and a check lamp 922C, and aliquid crystal display unit 922D for displaying various information bycharacters. The liquid crystal display unit 922D suitably displays, forexample, information of an operation input, an error message, and soforth.

The operation panel 920 further has provided thereon a plurality ofautomatic reading mode setting switches 924A and 924B each serving asinsertion mode selection means for selectively setting one of aplurality of (two including a mode 1 and a mode 2 here) automaticreading modes, a manual insertion setting switch 924C serving asinsertion mode selection means for setting a manual insertion mode, astart switch 924D for starting the image reading apparatus, and a stopswitch 924E for stopping the image reading apparatus. In order to startthe apparatus, one of the mode 1, the mode and the manual insertion modeis set, and then the start switch 924D will be operated.

The operation panel 920 further has provided thereon an original sizeinputting switch 924F, a reading concentration setting switch 924G, areading density setting switch 924H, a landscape switch 924J, a halftone (half tone) setting switch 924K, and the original selection switch(paper reading selection means) 924L. The original selection switch 924Lis a switch by which it can be set whether both face reading of anoriginal should be performed or one face reading only of the front faceor the rear face should be performed.

4-2. Construction of the Control System

FIG. 32 schematically shows the mechanical components described aboveand control sections for controlling the mechanical components.Referring to FIG. 32, a control section 930 includes a mechanicalsection control means 932 including a control circuit for controllingmechanical operations of the mechanical components, and image readingsystem control means 934 including a control circuit for controllingoperation of the image reading system. A pair of power source adjustmentsections 940A and 940B for transforming an external power source torequired voltages are connected to the image reading system controlmeans 934.

The mechanical section control means 932 controls operation of thetransport systems (that is, the paper supply mechanism 200, the papertransport mechanism 300, the paper stacking mechanism 500 and so forth)and the heater of the lamp unit and an invertor of the fluorescent lampin accordance with an instruction signal received by way of the imagereading system control means 934 and detection information from thevarious sensors of the mechanical components. The mechanical sectioncontrol means 932 also controls operation of a cooling fan 936 for thecontrol section 930 itself. The paper supply hopper position controlmeans (motor control means) 280, the pick clutch control means 250serving as paper supply roller driving mechanism control means, theseparation clutch control means 858 and the roller driving mechanismcontrol means 350 described hereinabove are included in the mechanicalsection control means 932.

The image reading system control means 934 controls operation of CCDdriver units of the first optical image reading unit 412 and the secondoptical image reading unit 414, a video circuit and a rear face readingboard 944 and outputting to an outputting interface board 938 inresponse to setting information of the operation panel 920 andinformation from the mechanical section control means 932. The imageinformation extraction control means 440, the paper leading enddetection circuit 450, the paper trailing end detection circuit 451 andthe discrimination mark image erasure means 460 described hereinaboveare provided in the image reading system control means 934.

Where an endorser (endorsing printer) 942 is provided in the proximityof the terminal end of the paper transport path 310 as shown in FIG. 7,also a driver for the endorser 942 is controlled by the image readingsystem control means 934 as seen from FIG. 32. Also where an extensionmemory board and/or an auxiliary printed circuit board (IPC-2) areprovided, they are controlled by the image reading system control means934.

4-3. Operation

Operations of the hopper motor 242, the pick clutch 238, the separationclutch 854 and the transport motor 342 and control by the imageinformation extraction control means 440 proceed, for example, in such amanner as illustrated in time charts of FIGS. 25 to 30.

First, control of the hopper motor 242 will be described. Upon startingof the control, control of an initialization mode is performed as seenfrom FIG. 25. In particular, in response to an operation startinginstruction (that is, a control starting instruction) for the imagereading apparatus such as, for example, throwing in of a power source tothe apparatus, the hopper motor 242 is rotated in a direction to lowerthe hopper table 212. Then, when the hopper table 212 comes to itslowermost position, the bottom sensor 622 switches from an off-state(open) to an on-state (closed), and the hopper motor 242 stops inresponse to such detection signal of the bottom sensor 622. Naturally,the control is not performed if, upon reception of the control startinginstruction, the hopper table 212 is already at the lowermost positionand the bottom sensor 622 is in an on-state (closed).

The control of the hopper motor 242 after this is different between anautomatic reading mode and the manual insertion mode in response tosetting information of the switches.

In particular, if paper sheets 42 are accommodated into the hopper table212 and a switch operation (depression of the start button) for anautomatic reading mode is performed, then the hopper motor 242 isrotated in a direction to raise the hopper table 212 as seen from FIG.26. Then, when the top of the paper sheets 40 in the hopper table 212rises from a position (bottom position) corresponding to the lowermostposition of the hopper table 212, whereupon the hopper empty sensor 610is turned on ("presence of a paper sheet"), to a prescribed height atwhich the paper supply sensor 612 is turned on ("presence of a papersheet").

When the hopper table 212 is raised by a little distance after the papersupply sensor 612 is turned on, the hopper motor 242 is stopped.Thereafter, image reading is performed while paper supplying andtransporting operations are performed. During the process, as the papersheets 40 are supplied, the height of the top of the stack of papersheets 40 decreases. Consequently, the paper supply sensor 612 is turnedoff finally, and in response to this, the hopper motor 242 is rotated inthe direction to raise the hopper table 212.

Then, as the height of the top of the stack of paper sheets 40 in thehopper table 212 rises again, it finally reaches the prescribed height,whereupon the paper supply sensor 612 is turned on ("presence of a papersheet"). While such a sequence of operations as described above isrepeated to control the height of the top of the paper sheets within afixed range, image reading operation is performed together with papersupplying and transporting operations.

On the other hand, if a switch operation for the manual insertion mode(depression of the manual insertion button) is performed, then thehopper motor 242 is rotated in the direction to raise the hopper table212 as seen from FIG. 27. Then, when the hopper table 212 is raiseduntil the height of the top end thereof comes to a prescribed height,then the paper supply sensor 612 is turned on ("presence of a papersheet"). When the hopper table 212 is further raised a little after thepaper supply sensor 612 is turned on, the hopper motor 242 is stopped.Thereafter, the hopper motor 242 is kept stopped and the hopper table212 keeps the position. Then, manual insertion of a paper sheet isperformed as can be seen also from an on/off condition of the hopperempty sensor 610.

Subsequently, operations of the pick clutch 238, the separation clutch854 and the transport motor 342 and control by the image informationextraction control means 440 will be described together with operationof the hopper motor 242. Referring to FIG. 28, paper sheets 40 are firstaccommodated into the paper supply hopper 210 and a start command toinstruct starting of image reading is developed (point T1). At thisinitial stage, since the paper supply hopper 210 is not at the papersupply position, the paper supply sensor 612 is in an off-state. Thehopper empty sensor 610 also provides a signal indicating absence of apaper sheet.

Since the paper supply sensor 612 is in an off-state, the hopper motor242 is rendered operative to raise the paper supply hopper 210 to thepaper supply position (point T2). Consequently, the paper supply sensor612 is turned on. As a result, the hopper motor 242 is stopped, and thepick clutch 238 and the separation clutch 854 are engaged. Thereafter,the transport motor 342 is started (point T3) after a small time lag (30ms in the example shown) until the pick clutch 238 and the separationclutch 854 are engaged firmly. By the operation of the transport motor342, the pick rollers 220 and the separation roller 820 are rotated byway of the pick clutch 238 and the separation clutch 854 to supply andtransport a first paper sheet.

The transport motor 342 can be selectively set to one of a low speedmode of a velocity V₁ (for example, 12 to 13 cm/s), a high speed mode ofanother velocity V₂ (for example, about 50 cm/s) and an intermediatespeed mode (mid speed mode) of an intermediate velocity between them.For the first paper sheet upon starting of paper supply, the transportmotor 342 operates in the low speed mode. Accordingly, also thetransportation speeds of the pick rollers 220 and the separation roller820 are low.

When the leading end of the paper sheet being transported in this mannerpasses the transport sensor 614, the transport sensor 614 detects thisand is turned on (point T4), and the pick clutch 238 is disengaged. Atthis point of time, the paper sheet is already at a position at which itcan be driven by the separation roller 820, and consequently, the papersheet is thereafter driven by the separation roller 820.

Then, when the leading end of the paper sheet being transported passesthe transport sensor 616, the transport sensor 616 detects this and isturned on (point T5), and the separation clutch 854 is disengaged. Atthis point of time, the paper sheet is already at a position at which itcan be driven by the transport roller 320, and consequently, the papersheet is thereafter driven by the transport roller 320. Thereafter, thepaper sheet is successively driven by the succeeding transport rollers322 to 328. At the point of time T5, since the transport motor 342 is inthe low speed mode, the transportation velocity of the transport roller320 itself is low.

The transport sensor 616 serves also as a sensor for detecting a readingtiming, and when the passage of the leading end of the paper sheet isdetected by the transport sensor 616, a read command is developed inresponse to the detection (point T6). Upon reception of the readcommand, the transport motor 342 is accelerated from the low speed mode(velocity V₁) to the high speed mode (velocity V₂). Accordingly, alsothe speed of rotation of the transport rollers 320 to 328, that is, thetransportation speed, increases until high speed transportation isreached.

Then, at a point of time T7 after lapse of a predetermined time t₃ afterthe leading end of the paper sheet passes the transport sensor 616, thefirst optical image reading unit 412 for reading information of thefront face of the paper sheet is put into a reading condition.Thereafter, at another point of time T8 after lapse of anotherpredetermined time t₄ after the leading end of the paper sheet passesthe transport sensor 616, the second optical image reading unit 414 forreading information on the rear face of the paper sheet is put into areading condition. In particular, each video gate (not shown) of thevideo circuit board 438 is put into an on-state.

It is to be noted that the predetermined times t₃ and t₄ are timesrequired for a paper sheet to pass from the transport sensor 616 to thereading points 412A and 414A of the optical image reading units 412 and414, respectively, and are given, from the distances L₁ and L₂ from thetransport sensor 616 to the reading points 412A and 414A and thetransportation speed V₂ by the transport roller 320, by the followingequations, respectively;

    t.sub.3 =L.sub.1 /V.sub.2, t.sub.4 =L.sub.2 /V.sub.2

During such image reading (at points of time T9 and T10), the transportsensors 614 and 616 are switched from on to off when the trailing end ofthe paper sheet passes the transport sensors 614 and 616, respectively.

Then, in each of the optical image reading units 412 and 414, when atime t₅ required for image reading passes (point T11 or T12), the videogate is switched from on to off, thereby completing reading (ReadComplete). It is to be noted that the time t₅ is given as a productbetween the reading line number and the integration time (t₅ =readingline number×integration time).

In this manner, while the first paper sheet is transported in the highspeed mode by the transport rollers 320 to 328, image reading of thefront face and the rear face of the paper sheet is performed by theoptical image reading units 412 and 414, respectively, and thereafter,the paper sheet is driven by the paper transport roller 328 and stackedinto the paper stacker 510.

After reading of the first paper sheet is completed, a start command isdeveloped immediately, and in response to the start command,transportation and reading of a second paper sheet are started. In theoperation for the second or following paper sheet, the image readingapparatus operates in such a manner as illustrated in FIG. 29.

In particular, in the present example, since the paper supply hopper 210is at the paper supply position (that is, the paper supply sensor 612 isin an on-state) when the start command is instructed (point T13), thepick clutch 238 and the separation clutch 854 are engaged simultaneouslywith the instruction of the start command. Since the transport motor 342continues to operate in the high speed mode, the pick roller 220 and theseparation roller 820 are rotated at a comparatively high speed due tothe engagement of the clutches 238 and 854 to transport the second papersheet. Naturally, in this instance, also the transport rollers 320 to328 are being rotated by the transport motor 342.

Thereafter, transportation and reading of the second paper sheet areperformed substantially in a similar manner to the first paper sheet.However, in transportation and reading of the second or following papersheet, since the transport motor 342 is operating in the high speed modefrom the beginning, the transport motor 342 is controlled to temporarilylower the speed thereof at a point of time when the main element fordriving the paper sheet changes over from the separation roller 820 tothe transport roller 320, different from the transportation and readingof the first paper sheet.

In particular, when the leading end of the second paper sheet which issupplied and transported at a comparatively high speed by the pickroller 220 and the separation roller 820 passes the transport sensor614, the transport sensor 614 detects this and is turned on (point T15).Consequently, the pick clutch 238 is disengaged and the paper sheet isthereafter driven by the separation roller 820.

Then, when the leading end of the second paper sheet passes thetransport sensor 616, the transport sensor 616 detects this and isturned on (point T19), and the separation clutch 854 is disengaged.Around the point of time T19 (between the points of time T17 to T20),the speed of the transport motor 342 is reduced temporarily from thehigh speed mode to the intermediate speed mode.

Such speed reduction control is started at a point of time T16 when arequired time elapses after the transport sensor 614 is turn on (at apoint of time before the leading end of the paper sheet passes thetransport sensor 616) and is performed by holding, after the point oftime T17 at which the speed drops to an intermediate speed, theintermediate speed till a point of time T20 at which a predeterminedtime (for example, 50 ms) elapses after the point of time T17.

Due to the speed reduction control, when the main element for drivingthe paper sheet changes over from the separation roller 820 to thetransport roller 320, the transportation speed of the separation roller820 and the transport roller 320 is suppressed, and consequently,changing over from the separation roller 820 to the transport roller 320proceeds smoothly. This reduces a cause of a trouble such as paperjamming.

Within the period, a read command is developed (point T18), andsimilarly as in transportation of the first paper sheet, the firstoptical image reading unit 412 for reading information of the front faceof a paper sheet is put into a reading condition at a point of time T21at which the predetermined time t₃ elapses after the leading end of thepaper sheet passes the transport sensor 616. Then, at another point oftime T22 when the predetermined time t₄ elapses after the leading end ofthe paper sheet passes the transport sensor 616, the second opticalimage reading unit 414 for reading information of the rear face of apaper sheet is put into a reading condition. In particular, each videogate (not shown) of the video circuit board 438 is put into an on-state.It is to be noted that the predetermined times t₃ and t₄ mentioned aboveare given similarly as described hereinabove.

During such image reading, the transport sensors 614 and 616 are changedover from an on-state to an off-state (points T23 and T24) as thetrailing end of the paper sheet passes the transport sensors 614 and616, respectively.

Then, in each of the optical image reading units 412 and 414, the videogate is changed over from an on-state to an off-stage to complete thereading (Read Complete) when the time t₅ required for image readingelapses. Also the time t₅ is given similarly as described hereinabove.

In this manner, while the second or following paper sheet is transportedin the high speed mode by the transport rollers 320 to 328, imagereading of the front face and the rear face of the paper sheet isperformed by the optical image reading units 412 and 414, respectively,and thereafter, the paper sheet is driven by the paper transport roller328 and the paper discharge roller and stacked into the paper stacker510.

If the paper supply sensor 612 is turned off as a result of reduction inquantity of the paper sheets 40 in the paper supply hopper 210 (pointT14 in FIG. 29), then the hopper motor 242 is rendered operative at apoint of time (T27) at which the operations of the pick roller 220 andthe separation roller 820 and the speed reduction control of thetransport motor 342 are completed to raise the paper supply hopper 210to the paper supply position (point T2). Such height control of thepaper supply hopper 210 is performed each time the paper supply sensor612 is turned off as a result of reduction in quantity of the papersheets 40 while the paper supplying and transporting operations areperformed.

Then, when the paper sheets 40 in the paper supply hopper 210 arereduced in quantity until the paper supply hopper 210 becomes empty, thehopper empty sensor 610 changes over from an off-state ("paper present")to an on-state ("paper absent") (point T28) as seen from FIG. 30, andthen the transport sensor 616 changes over from an on-state ("duringpaper passage") to an off-state ("completion of paper passage") (pointT29). Thereafter, the video gate of the second optical image readingunit 414 on the downstream side of the transport path is changed overfrom an on-state to an off-state and simultaneously the read command ischanged over from an on-state to an off-state (point T30), and then thedischarge sensor 618 changes over from an on-state ("during paperpassage") to an off-state ("completion of paper passage") (point T31).The power supply to the transport motor 342 is cut to stop the transportmotor 342 after lapse of a predetermined time t₈ after the dischargesensor 618 changes over to an off-state. The predetermined time t₈corresponds to a time within which a paper sheet 40 is transported fromthe discharge sensor 618 to the stacker 500.

It is to be noted that, if a paper sheet to be read requires imagereading of only one face thereof and it is intended to read, forexample, only the front face of the paper sheet, when reading of thevideo gate of the first optical image reading unit 412 in FIGS. 28 and29 comes to an end, it is determined that reading for the paper sheet iscompleted (Read Complete), and next control is started immediately.

Since transportation and image reading of paper sheets is performed inresponse to the hopper empty sensor 610, the paper supply sensor 612,the transport sensors 614 and 616 and the discharge sensor 618 in thismanner, the image reading operation can be performed appropriately inaccordance with a transportation condition of a paper sheet, which issuitable to high speed image reading. Further, if paper jamming (paperjamming) should occur intermediately of the paper transport path, thiscan be detected promptly and the operation of the image readingapparatus can be stopped immediately.

Further, since the control timings by the roller driving mechanismcontrol means 350 and the image information extraction control means 440are synchronized with each other, even if the processing speed for imagereading is increased, the paper transportation operation and the imagereading operation can be performed with certainty.

Furthermore, since reading of information of the front face of a papersheet 40 is performed optically by the first optical image reading unit412 and reading of information of the rear face of the paper sheet 40 isperformed optically by the second optical image reading unit 414,reading of image information on the opposite faces of the paper sheet 40can be performed rapidly, and the processing speed of a double-sideoriginal is improved significantly.

Further, with the image reading apparatus of the present embodiment, thefollowing advantages can be achieved due to its structuralcharacteristics.

In particular, since the paper transport path 310 connected to the papersupply mechanism 200 is constituted from the inclined transport path 312and the paper reversing transport path 314 without involving ahorizontal transport path, the paper transport path 310 requires acomparatively small depthwise space, and accordingly, there is anadvantage in that the image reading apparatus can be reduced in size asmuch. Further, there is another advantage in that a paper sheet can betransported rapidly from the paper supply mechanism 200 to the stackermechanism 300 and image reading can be performed at a high speed.Naturally, the reduction in space allows an increase in size of thepaper sheet hopper or the paper stacker, which allows reading of a papersheet of a greater size.

By the way, referring back to FIG. 3, analog video signals from the CCDarrays 436AA and 436AB of the image reading units 412 and 414 areamplified by the amplification circuits 64A and 64B, respectively, andthe analog video signals of the outputs of the amplification circuits64A and 64B in portions (bits) in which, for example, the photosensitiveportions of the CCD arrays 436AA and 436AB are masked are sampled andheld by the black level setting circuits (sample hold circuits) 71A and71B and are connected as reference signals for a black level to thelower limit sides (VRB) of the analog to digital conversion circuits 60Aand 60B, respectively. For a reference signal for a white level, asignal obtained by digital to analog conversion of a white level valueof each bit of each line obtained by scanning in the last scanning cycleand stored in the memory circuit 72-1 or 72-2 by the digital to analogconversion circuit 62A or 62B is used and connected to the upper limitside (VRT) of the analog to digital conversion circuit 60A or 60B.

Consequently, the analog to digital conversion circuit 60A or 60Boutputs a multiple value digital signal on the scale of 256 gradationsbetween the reference level (VRT) for white and the reference level(VRB) for black. In this instance, for the reference level for white, ananalog value of a white level produced with reference to a white levelobtained by scanning of the image in the last scanning cycle is used,and for the reference value for black, an analog value at a dot at whichthe photosensitive element of the CCD array 436AA or 436AB is masked isused.

It is to be noted that, in this instance, for example, in such a casethat paper sheets whose ground color is white have been read till nowand blue print paper sheets of a different ground color are to be readsubsequently, the white level value to be provided to the analog todigital conversion circuit 60 is varied in response to an instructionsignal from the MPU circuit 150 by the white level informationcorrection circuit 70. In particular, as seen from FIGS. 14 to 20, whitelevel information stored in the memory circuit 72-1 (or 72-2) or thestorage area 72-11 (or 72-12) is taken out and stored into the register73-1 (or 73-2) or 73, and then the output of the register 73-1 (or 73-2)or 73 is multiplied by m by the data magnification variation circuit 74.Then, the output of the data magnification variation circuit 74 isselected by the selection circuit 75b and then processed by requiredprocessing by the white level algorithm circuit 77, and then the whitelevel of the thus varied magnification is stored into the other memorycircuit 72-2 (or 72-1) or the other storage area 72-12 (or 72-11) by wayof the selection circuit 75c. Then, the white level of the variedmagnification is used as a conversion reference of the analog to digitalconversion circuit 60.

Thereafter, so far as such blue print paper sheets are used, the whitelevel from the memory circuit 72-2 (or 72-1) or the storage area 72-12(or 72-11) is extracted, and now, the output of the memory circuit 72-2(or 72-1) or the storage area 72-12 (or 72-11) is inputted by way of theselection circuit 75b to the white level algorithm circuit 77. Then, theprocessing described above is performed subsequently by the white levelalgorithm circuit 77 so that the white level value may have anappropriate value to update the white level.

Consequently, even in such a case that paper sheets whose ground coloris white have been read till now and blue print paper sheets of adifferent ground color are to be read subsequently, the white levelinformation correction apparatus copes with this sufficiently and canperform analog to digital conversion with a high degree of accuracy.

Then, the image signal after digital conversion by the analog to digitalconversion circuit 60A or 60B is transferred to the image processingsection 68A or 68B for next image processing such as, for example,emphasis processing to emphasize the contrast between white and black or"dither processing; binary digitization processing" for a net pointimage such as a photograph image as described hereinabove.

Further, in each of the image data processing systems D1 and D2, digitalinformation obtained from the analog to digital conversion circuit 60Aor 60B is sent, after it is processed by emphasis processing and/orbinary digitization processing by the image processing section 68A or68B, to the outputting section 90 as seen from FIG. 3, and paper frontface data and paper rear face data are transferred from the outputtingsection 90 to the host computer (not shown).

Upon such transfer, data (paper front face data) from the firstoperating image reading unit 412 from one of the first optical imagereading unit 412 and the second optical image reading unit 414 fromwhich paper image information is to be read out first are firsttransferred successively by way of a data transfer line. Meanwhile, data(paper rear face data) from the later operating image reading unit 414from one of the first optical image reading unit 412 and the secondoptical image reading unit 414 from which paper image information is tobe read out later are temporarily stored into the DRAM 92, and, afterthe data from the first operating image reading unit 412 are transferredcompletely, the stored data from the later operating image reading unit414 are successively transferred at a rate higher than the transfer rateof the data from the first operating image reading unit 412 by way ofanother data transfer line.

Consequently, even if image reading by the later operating image readingunit 414 is started before image reading by the first operating imagereading unit 412 is completed, data within the overlapping period can beheld with certainty. Besides, data from the later operating imagereading unit 414 from which data are to be transferred later can betransferred rapidly to the host computer side.

Accordingly, even where the image reading units 412 and 414 are disposedin the proximity of the paper transport path in order to achieveminimization, reduction in weight and compaction of the apparatus, dataof the front and rear faces of a paper sheet can be transferred to thehost computer side before the paper sheet is discharged to the stackingmechanism 500. Consequently, even if paper sheets are successivelytransferred at a high speed while achieving minimization, reduction inweight and compaction of the apparatus, data of the front and rear facesof each paper can be read and transferred to the host computer sidesatisfactorily.

In this instance, the paper leading end detection circuit 450 detectsthe leading end of a paper sheet based on a paper end detected for thefirst time, and then when the MPU circuit 150 receives such paperleading end detection signal as an interruption requesting (IRQ) signalfrom the paper leading end detection circuit 450, the MPU circuit 150develops, in response to the interruption requesting (IRQ) signal, acommand signal to read the front face of the paper sheet. As a result,also the selection circuit 96 is switched to the paper front face dataside.

Meanwhile, the paper trailing end detection circuit 451 detects thetrailing end of the paper sheet based on a paper end detected for thesecond time, and then when the MPU circuit 150 receives such papertrailing end detection signal as an interruption requesting (IRQ) signalfrom the paper trailing end detection circuit 451, the MPU circuit 150develops, in response to the interruption requesting (IRQ) signal, acommand signal to read the rear face of the paper sheet. As a result,also the selection circuit 96 is switched to the paper rear face dataside.

Where the paper leading end detection circuit 450 and the paper trailingend detection circuit 451 of such circuit construction as describedabove are employed, the leading end and the trailing end of a papersheet can be detected with certainty with a common circuit constructionand with a simple construction. Consequently, reading timings of paperfront face data and paper rear face data or reading switching timingsbetween them can be controlled precisely irrespective of the type of apaper sheet being transported. As a result, it is comparatively possiblefor the image reading apparatus to allow paper sheets of various sizesto be transported to read information on them.

c. Other Embodiment

Referring now to FIG. 33, there is shown, in block diagram, a dataprocessing system according to another preferred embodiment of thepresent invention. The data processing system is applied to an apparatus(image scanner) for reading color information of the opposite faces ofan original. To this end, the data processing system shown includes afirst image data processing system D11 for processing color image dataread by first optical image reading units 412RA, 412GA and 412BA whichare provided for reading information of three primary colors (red (R),green (G) and blue (B)) on a front face of a paper sheet, and a secondimage data processing system D12 for processing image data read bysecond optical image reading units 414RB, 414GB and 414BB which areprovided for reading information of three primary colors (red (R), green(G) and blue (B)) on a rear face of a paper sheet.

The first image data processing system D11 includes CCD arrays (notshown) of the first optical image reading units 412RA, 412GA and 412BA,amplification circuits 64RA, 64GA and 64BA, sample hold circuits 66RA,66GA and 66BA, analog to digital conversion circuits 60RA, 60GA and60BA, and image processing sections 68RA, 68GA and 68BA. The secondimage data processing system D12 includes CCD arrays (not shown) of thesecond optical image reading units 414RB, 414GB and 414BB, amplificationcircuits 64RB, 64GB and 64BB, sample hold circuits 66RB, 66GB and 66BB,analog to digital conversion circuits 60RB, 60GB and 60BB, and imageprocessing sections 68RB, 68GB and 68BB.

It is to be noted that the optical image reading units, theamplification circuits, the sample hold circuits, the analog to digitalconversion circuits and the image processing sections may be similar tothose described hereinabove in connection with the first embodiment, andoverlapping description thereof is omitted herein to avoid redundancy.

Accordingly, analog video signals from the CCD arrays of the opticalimage reading units 412RA, 412GA, 412BA and 414RB, 414GB, 414BB areamplified by the amplification circuits 64RA, 64GA, 64BA and 64RB, 64GB,64BB and then converted into digital signals by the analog to digitalconversion circuits 60RA, 60GA, 60BA and 60RB, 60GB, 60BB, respectively,whereafter they are processed by emphasis processing, binarydigitization processing and some other necessary processing by the imageprocessing sections 68RA, 68GA, 68BA and 68RB, 68GB, 68BB, respectively,and then sent to an outputting section 90. Consequently, paper frontface three primary color data and paper rear face three primary colordata are transferred from the outputting section 90 to a host computer(not shown).

Referring now to FIG. 34, the outputting section 90 includes a latchcircuit 91, DRAMs (buffer storage apparatus) 92GA, 92BA, 92RB, 92GB and92BB, memory control sections 93GA, 93BA, 93RB, 93GB and 93BB, read databuffers 94GA, 94BA, 94RB, 94GB and 94BB, timing production sections95GA, 95BA, 95RB, 95GB and 95BB, and a selection circuit 96.

The latch circuit 91 latches paper front face first color data VDRA andfront face first color timing signals VGRA, HGRA and VCLKRA from thefirst image data processing system D11 for processing data of the firstcolor (red) of the front face of a paper sheet, and notifies it to anoutput control circuit 100 that paper front face first color data andfront face first color timing signals have been latched by the latchcircuit 91. It is to be noted that a flip-flop is used for the latchcircuit 91.

Meanwhile, the timing signal VGGA is a horizontal direction (directionof a line; main scanning direction) gate signal, and the timing signalHGGA is a vertical direction (paper transporting direction; sub scanningdirection) gate signal. In response to the timing signals VGGA and HGGA,one bit of a picture element in one line for the first color of thefront face of a paper sheet scan be extracted. Further, the timingsignal VCLKGA is a clock signal which defines the transfer rate of frontface first color data.

The DRAM 92GA is a memory circuit for storing paper front face secondcolor (green) data VDGA, and the memory control section 93GA controlsstorage and reading out into and from the DRAM 92GA. In particular, thememory control section 93GA is constructed as a DMAC (dynamic memoryaccess control) and controls the DRAM 92GA such that paper front facesecond color data VDGA sent thereto are stored into the DRAM 92GA and,after paper front face first color data VDRA are received for one fullpaper sheet, the paper front face second color data VDGA are read outfrom the DRAM 92GA (in this instance, read out in units of one bit)between successive storing operations of subsequent paper front facesecond color data VDGA into the DRAM 92GA.

The read data buffer 94GA temporarily stores paper front face secondcolor data VDGA read out partially from the DRAM 92GA between successivestoring operations of paper front face second color data VDGA into theDRAM 92GA and produces collective data to be sent out.

It is to be noted that the the rates at which data are read out from theDRAM 92GA and the read data buffer 94GA are set higher than the writingrate, that is, the transfer rate of front face first color data to thehost computer.

The timing production section 95GA produces timing signals VGGA, HGGAand VCLKGA. Also in this instance, the timing signal VGGA is ahorizontal direction (direction of a line; main scanning direction) gatesignal while the timing signal HGGA is a vertical direction (papertransporting direction; sub scanning direction) gate signal, and inresponse to those signals, one bit of a picture element in one line ofthe paper front face second color can be extracted. Further, the timingsignal VCLKGA is a clock signal which defines the front face secondcolor data transfer rate. In this instance, the rate of the front facesecond color timing signal VCLKGA is set higher than that of the frontface first color timing signal VCLKRA. Since the rate of the front facesecond color timing signal VCLKGA is set in this manner and the datareading out rates from the DRAM 92GA and the read data buffer 94GA areset as described above, front face second color data are transferred ata rate higher than that of front face first color data.

The DRAM 92BA is a memory circuit for storing paper front face thirdcolor (blue) data VDBA, and the memory control section 93BA controlsstorage and reading out into and from the DRAM 92BA. In particular, thememory control section 93BA is constructed as a DMAC (dynamic memoryaccess control) and controls the DRAM 92BA such that paper front facethird color data VDBA sent thereto are stored into the DRAM 92BA and,after paper front face second color data VDGA are received for one fullpaper sheet, the paper front face third color data VDBA are read outfrom the DRAM 92BA (also in this instance, read out in units of one bit)between successive storing operations of subsequent paper front facethird color data VDBA into the DRAM 92BA.

The read data buffer 94BA temporarily stores paper front face thirdcolor data VDBA read out partially from the DRAM 92BA between successivestoring operations of paper front face third color data VDBA into theDRAM 92BA and produces collective data to be sent out.

It is to be noted that the the rates at which data are read out from theDRAM 92BA and the read data buffer 94BA are set higher than the transferrate of front face second color data to the host computer.

The timing production section 95BA produces timing signals VGBA, HGBAand VCLKBA. Also in this instance, the timing signal VGBA is ahorizontal direction (direction of a line; main scanning direction) gatesignal while the timing signal HGBA is a vertical direction (papertransporting direction; sub scanning direction) gate signal, and inresponse to those signals, one bit of a picture element in one line ofthe paper front face second color can be extracted. Further, the timingsignal VCLKBA is a clock signal which defines the front face third colordata transfer rate. In this instance, the rate of the front face thirdcolor timing signal VCLKBA is set higher than those of the front facefirst color timing signal VCLKRA and the front face second color timingsignal VCLKGA. Since the rate of the front face third color timingsignal VCLKBA is set in this manner and the data reading out rates fromthe DRAM 92BA and the read data buffer 94BA are set as described above,front face third color data are transferred at a rate higher than thoseof front face first color data and front face second color data.

The DRAM 92RB is a memory circuit for storing paper rear face firstcolor (red) data VDRB, and the memory control section 93RB controlsstorage and reading out into and from the DRAM 92RB. In particular, thememory control section 93RB is constructed as a DMAC (dynamic memoryaccess control) and controls the DRAM 92RB such that paper rear facefirst color data VDRB sent thereto are stored into the DRAM 92RB and,after paper front face third color data VDBA are received for one fullpaper sheet, the paper rear face first color data VDRB are read out fromthe DRAM 92RB (also in this instance, read out in units of one bit)between successive storing operations of subsequent paper rear facefirst color data VDRB into the DRAM 92RB.

The read data buffer 94RB temporarily stores paper rear face first colordata VDRB read out partially from the DRAM 92RB between successivestoring operations of paper rear face first color data VDRB into theDRAM 92RB and produces collective data to be sent out.

It is to be noted that the the rates at which data are read out from theDRAM 92RB and the read data buffer 94RB are set higher than the transferrates of front face first to third color data to the host computer.

The timing production section 95RB produces timing signals VGRB, HGRBand VCLKRB. Also in this instance, the timing signal VGRB is ahorizontal direction (direction of a line; main scanning direction) gatesignal while the timing signal HGRB is a vertical direction (papertransporting direction; sub scanning direction) gate signal, and inresponse to those signals, one bit of a picture element in one line ofthe paper front face second color can be extracted. Further, the rearface first color timing signal VCLKRB is a clock signal which definesthe rear face first color data transfer rate. In this instance, the rateof the rear face first color timing signal VCLKRB is set higher thanthose of the front face first to third color timing signals. Since therate of the rear face first color timing signal VCLKRB is set in thismanner and the data reading out rates from the DRAM 92RB and the readdata buffer 94RB are set as described above, rear face first color dataare transferred at a rate higher than those of front face first to thirdcolor data.

The DRAM 92GB is a memory circuit for storing paper rear face secondcolor (green) data VDGB, and the memory control section 93GB controlsstorage and reading out into and from the DRAM 92GB. In particular, thememory control section 93GB is constructed as a DMAC (dynamic memoryaccess control) and controls the DRAM 92GB such that paper rear facesecond color data VDGB sent thereto are stored into the DRAM 92GB and,after paper rear face first color data VDRB are received for one fullpaper sheet, the paper rear face second color data VDGB are read outfrom the DRAM 92GB (in this instance, read out in units of one bit)between successive storing operations of subsequent paper rear facesecond color data VDGB into the DRAM 92GB.

The read data buffer 94GB temporarily stores paper rear face secondcolor data VDGB read out partially from the DRAM 92GB between successivestoring operations of paper rear face second color data VDGB into theDRAM 92GB and produces collective data to be sent out.

It is to be noted that the the rates at which data are read out from theDRAM 92GB and the read data buffer 94GB are set higher than the transferrates of rear face first color data and front face first to third colordata to the host computer.

The timing production section 95GB produces timing signals VGGB, HGGBand VCLKGB. Also in this instance, the timing signal VGGB is ahorizontal direction (direction of a line; main scanning direction) gatesignal while the timing signal HGGB is a vertical direction (papertransporting direction; sub scanning direction) gate signal, and inresponse to those signals, one bit of a picture element in one line ofthe paper front face second color can be extracted. Further, the rearface second color timing signal VCLKGB is a clock signal which definesthe rear face second color data transfer rate. In this instance, therate of the rear face second color timing signal VCLKGB is set higherthan that of the rear face first color timing signal VCLKRB. Since therate of the rear face second color timing signal VCLKGB is set in thismanner and the data reading out rates from the DRAM 92GB and the readdata buffer 94GB are set as described above, rear face second color dataare transferred at a rate higher than those of rear face first colordata and front face first to third color data.

The DRAM 92BB is a memory circuit for storing paper rear face thirdcolor (blue) data VDBB, and the memory control section 93BB controlsstorage and reading out into and from the DRAM 92BB. In particular, thememory control section 93BB is constructed as a DMAC (dynamic memoryaccess control) and controls the DRAM 92BB such that paper rear facethird color data VDBB sent thereto are stored into the DRAM 92BB and,after paper rear face second color data VDGB are received for one fullpaper sheet, the paper rear face third color data VDBB are read out fromthe DRAM 92BB (also in this instance, read out in units of one bit)between successive storing operations of subsequent paper rear facethird color data VDBB into the DRAM 92BB.

The read data buffer 94BB temporarily stores paper rear face third colordata VDBB read out partially from the DRAM 92BB between successivestoring operations of paper rear face third color data VDBB into theDRAM 92BB and produces collective data to be sent out.

It is to be noted that the the rates at which data are read out from theDRAM 92BB and the read data buffer 94BB are set higher than the transferrates of rear face first and second color data and front face first tothird color data to the host computer.

The timing production section 96BB produces timing signals VGBB, HGBBand VCLKBB. Also in this instance, the timing signal VGBB is ahorizontal direction (direction of a line; main scanning direction) gatesignal while the timing signal HGBB is a vertical direction (papertransporting direction; sub scanning direction) gate signal, and inresponse to those signals, one bit of a picture element in one line ofthe paper front face second color can be extracted. Further, the rearface third color timing signal VCLKBB is a clock signal which definesthe rear face third color data transfer rate. In this instance, the rateof the rear face third color timing signal VCLKBB is set higher thanthose of the rear face first and second color timing signals and thefront face first to third color timing signals. Since the rate of therear face third color timing signal VCLKBB is set in this manner and thedata reading out rates from the DRAM 92BB and the read data buffer 94BBare set as described above, rear face third color data are transferredat a rate higher than those of rear face first and second color data andfront face first to third color data.

The selection circuit 96 receives a control signal from the outputcontrol circuit 100 and selectively outputs paper front face first tothird color data and paper rear face first to third color data. Inparticular, the selection circuit 96 is switched so that paper frontface first to third color data are first transferred successively forone full paper sheet and then paper rear face first to third color dataare successively transferred for one full paper sheet.

The output control circuit 100 controls switching of the selectioncircuit 96 and controls the memory control sections 93GA, 93BA, 93RB,93GB and 93BB to successively transfer paper front face first to thirdcolor data and paper rear face first to third color data from theoutputting section 90 to the host computer.

Accordingly, it is recognized that the outputting section 90 includesfirst storage means (the DRAMs 92GA and 92BA) for storing data from thefirst optical image reading units 412RA, 412GA and 412BA, and secondstorage means (the DRAMs 92RB, 92GB and 92BB) for storing data from thesecond optical image reading units 414RB, 414GB and 414BB.

Also it is recognized that the outputting section 90 includes first datatransfer means (the latch circuit 91, memory control sections 93GA and93BA, timing production sections 95GA and 95BA, selection circuit 96 andso forth) for reading out stored data obtained from ones of the firstoptical image reading units 412RA, 412GA and 412BA and the secondoptical image reading units 414RB, 414GB and 414BB at a reading out ratehigher than the writing data, at which the stored data were stored, andsuccessively transferring the thus read out data by way of a datatransfer line, and second data transfer means (the memory controlsections 93RB, 93GB and 93BB, timing production sections 95RB, 95GB and95BB, selection circuit 96 and so forth) for reading out, after datastored in the first storage means have been transferred by the firstdata transfer means, stored data obtained from the other ones of thefirst optical image reading units 412RA, 412GA and 412BA and the secondoptical image reading units 414RB, 414GB and 414BB at a reading out ratehigher than the writing rate, at which the stored data were stored, andsuccessively transferring the thus read out data by way of the datatransfer line.

It is to be noted that, in the present embodiment, the transfer rate ofpaper front face data increases in order of the first to third colors,and also the transfer rate of paper rear face data increases in order ofthe first to third colors.

Accordingly, the outputting section 90 operates in such a manner asillustrated in FIGS. 35 and 36.

In particular, referring first to FIG. 35, since the selection circuit96 initially is in a switched condition to the paper front face firstcolor data side, paper front face first color data are transferredthrough the outputting section 90 (step B1). Then, if such transfer offront face first color data is completed, then the route of YES is takenat step B2, and the selection circuit 96 is switched to the paper frontface second color data side (step B3). Then at step B4, data are readout from the DRAM 92GA and stored into the read data buffer 94GA, andthe paper front face second data are transferred at a higher rate (stepB5). Then, the operations at steps B4 and B5 are repeated until afterthe DRAM 92GA becomes empty (step B6).

Thereafter, the selection circuit 96 is switched to the paper front facethird color data side (step B7). Then at step B8, data are read out fromthe DRAM 92BA and stored into the read data buffer 94BA, and the paperfront face third color data are transferred at another higher rate (stepB9). Then, the operations at step B7 and B8 are repeated until after theDRAM 92BA becomes empty (step B10).

Referring now to FIG. 35, the selection circuit 96 is thereafterswitched to the paper rear face first color data side (step B11). Thenat step B12, data are read out from the DRAM 92RB and stored into theread data buffer 94RB, and the paper rear face first color data aretransferred at a further higher rate (step B13). Then, the operations atsteps B12 and B13 are repeated until after the DRAM 92RB becomes empty(step B14).

Then, the selection circuit 96 is switched to the paper rear face secondcolor data side (step B15). Then at step B16, data are read out from theDRAM 92GB and stored into the read data buffer 94GB, and the paper rearface second color data are transferred at a still further higher rate(step B17). Then, the operations at step B16 and B17 are repeated untilafter the DRAM 92GB becomes empty (step B18).

Thereafter, the selection circuit 96 is switched to the paper rear facethird color data (step B19). Then at step B20, data are read out fromthe DRAM 92BB and stored into the read data buffer 94BB, and the paperrear face third color data are transferred at a yet further higher rate(step B21). Then, the operations at steps B20 and B21 are repeated untilafter the DRAM 92BB becomes empty (step B22).

Due to the construction described above, paper front face first to thirdcolor data and paper rear face first to third color data aresuccessively transferred to the host computer. In this instance, datatransferred later in time are transferred at a higher rate.

Accordingly, also in the data processing system of the presentembodiment, even if image reading by a later operating image readingunit is started before image reading by a first or earlier operatingimage reading unit is completed, data during the overlapping period oftime can be held with certainty, and besides, data from the lateroperating image reading unit which are to be transferred later can betransferred rapidly to the host computer side. Consequently, even wherethe image reading units are disposed in the proximity of the papertransport path in order to achieve minimization, reduction in weight andcompaction of the apparatus, data of the front and rear faces of a papersheet can be transferred to the host computer side before the papersheet is discharged to the stacking mechanism. Consequently, even ifpaper sheets are successively transferred at a high speed whileachieving minimization, reduction in weight and compaction of theapparatus, data of the front and rear faces of each paper sheet can beread and transferred to the host computer side satisfactorily.

d. Others

It is to be noted that, while, in the data processing systems accordingto embodiments described above, paper front face data are read andtransferred to the host computer prior to paper rear face data, thearrangement of the first optical image reading unit or units and thesecond optical image reading unit or units may be reversed so that paperrear face data may be read and transferred to the host computer prior topaper front face data.

The present invention is not limited to the specifically describedembodiment, and variations and modifications may be made withoutdeparting from the scope of the present invention.

What is claimed is:
 1. A data transfer method for an image readingapparatus which includes a first optical image reading unit located at alocation along a paper transport path for optically reading front faceimage information from a paper sheet transported along said papertransport path, and a second optical image reading unit located atanother location along said paper transport path for optically readingrear face image information from the paper sheet transported along saidpaper transport path, comprising the steps of:successively transferring,by way of a data transfer line, data from a first operating imagereading unit from one of said first optical image reading unit and saidsecond optical image reading unit from which paper image information isto be read out first; temporarily storing data from a later operatingimage reading unit from one of said first optical image reading unit andsaid second optical image reading unit from which paper imageinformation is to be read out later; and successively transferring,after the data from said first operating image reading unit have beentransferred, the stored data from said later operating image readingunit at a rate higher than the transfer rate at which the data from saidfirst operating image reading unit have been transferred.
 2. A datatransfer method for an image reading apparatus as claimed in claim 1,wherein the data from said later operating image reading unit are storedfor one full paper sheet.
 3. A data transfer method for an image readingapparatus as claimed in claim 1, wherein the data from said lateroperating image reading unit are held stored until the data from saidlater operating image reading unit are permitted to be transferredthrough said image reading apparatus after outputting of the data fromsaid first operating image reading unit for one full paper sheet hasbeen completed.
 4. A data transfer method for an image reading apparatusas claimed in claim 1, wherein completion of transfer of the data fromsaid first operating image reading unit is detected based on papertrailing end detection information.
 5. A data transfer apparatus for animage reading apparatus which includes a first optical image readingunit located at a location along a paper transport path for opticallyreading front face image information from a paper sheet transportedalong said paper transport path, and a second optical image reading unitlocated at another location along said paper transport path foroptically reading rear face image information from the paper sheettransported along said paper transport path, comprising:storage meansfor storing data from a later operating image reading unit from one ofsaid first optical image reading unit and said second optical imagereading unit from which paper image information is to be read out later;first data transfer means for successively transferring, by way of adata transfer line, data from a first operating image reading unit fromone of said first optical image reading unit and said-second opticalimage reading unit from which paper image information is to be read outfirst; and second data transfer means for successively transferring,after the data from said first operating image reading unit have beentransferred by said first data transfer means, the data from said lateroperating image reading unit stored in said storage means at a ratehigher than the data transfer rate at which data are transferred by saidfirst data transfer means by way of said data transfer line.
 6. A datatransfer apparatus for an image reading apparatus as claimed in claim 5,further comprising auxiliary storage means for storing partial paperimage information read out from said storage means between successivewriting operations of data into said storage means.
 7. An image readingapparatus with a data transfer apparatus, comprising:a first opticalimage reading unit located at a location along a paper transport pathfor optically reading front face image information from a paper sheettransported along said paper transport path; a second optical imagereading unit located at another location along said paper transport pathfor optically reading rear face image information from the paper sheettransported along said paper transport path; and a data transferapparatus for transferring paper image information from said firstoptical image reading unit and said second optical image reading unit;said data transfer apparatus including storage means for storing datafrom a later operating image reading unit from one of said first opticalimage reading unit and said second optical image reading unit from whichpaper image information is to be read out later, first data transfermeans for successively transferring, by way of a data transfer line,data from a first operating image reading unit from one of said firstoptical image reading unit and said second optical image reading unitfrom which paper image information is to be read out first, and seconddata transfer means for successively transferring, after the data fromsaid first operating image reading unit have been transferred by saidfirst data transfer means, the data from said later operating imagereading unit stored in said storage means at a rate higher than the datatransfer rate at which data are transferred by said first data transfermeans by way of said data transfer line.
 8. A data transfer method foran image reading apparatus which includes a first optical image readingunit located at a location along a paper transport path for opticallyreading front face image information from a paper sheet transportedalong said paper transport path, and a second optical image reading unitlocated at another location along said paper transport path foroptically reading rear face image information from the paper sheettransported along said paper transport path, comprising the stepsof:temporarily storing data from said first optical image reading unitand said second optical image reading unit; reading out the stored dataobtained from one of said first optical image reading unit and saidsecond optical image reading unit at a reading out rate higher than thewriting rate at which the stored data have been stored and successivelytransferring the thus read out data by way of a data transfer line; andreading out the stored data obtained from the other of said firstoptical image reading unit and said second optical image reading unit ata reading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of said data transfer line.
 9. A data transfer method for an imagereading apparatus as claimed in claim 8, wherein a plurality of data areobtained from each of said first optical image reading unit and saidsecond optical image reading unit.
 10. A data transfer apparatus for animage reading apparatus which includes a first optical image readingunit located at a location along a paper transport path for opticallyreading front face image information from a paper sheet transportedalong said paper transport path, and a second optical image reading unitlocated at another location along said paper transport path foroptically reading rear face image information from the paper sheettransported along said paper transport path, comprising:first storagemeans for storing data from said first optical image reading unit;second storage means for storing data from said second optical imagereading unit; first data transfer means for reading out the stored dataobtained from one of said first optical image reading unit and saidsecond optical image reading unit at a reading out rate higher than thewriting rate at which the stored data have been stored and successivelytransferring the thus read out data by way of a data transfer line; andsecond data transfer means for reading out, after the data stored insaid first storage means have been transferred by said first datatransfer means, the stored data obtained from the other of said firstoptical image reading unit and said second optical image reading unit ata reading out rate higher than the writing rate at which the stored datahave been stored and successively transferring the thus read out data byway of said data transfer line.
 11. An image reading apparatus with adata transfer apparatus, comprising:a first optical image reading unitlocated at a location along a paper transport path for optically readingfront face image information from a paper sheet transported along saidpaper transport path; a second optical image reading unit located atanother location along said paper transport path for optically readingrear face image information from the paper sheet transported along saidpaper transport path; and a data transfer apparatus for transferringpaper image information from said first optical image reading unit andsaid second optical image reading unit; said data transfer apparatusincluding first storage means for storing data from said first opticalimage reading unit, second storage means for storing data from saidsecond optical image reading unit, first data transfer means for readingout the stored data obtained from one of said first optical imagereading unit and said second optical image reading unit at a reading outrate higher than the writing rate at which the stored data have beenstored and successively transferring the thus read out data by way of adata transfer line, and second data transfer means for reading out,after the data stored in said first storage means have been transferredby said first data transfer means, the stored data obtained from theother of said first optical image reading unit and said second opticalimage reading unit at a reading out rate higher than the writing rate atwhich the stored data have been stored and successively transferring thethus read out data by way of said data transfer line.